CN104536076B - Method and apparatus for sequentially laminating optical films having polarizing films on rectangular panel - Google Patents

Abstract

The invention provides a method for bonding an optical film with a polarizing film and a rectangular panel. The method is a method of sequentially laminating an optical film laminate on a rectangular panel having a long side and a short side, using an optical film laminate with a carrier film, the optical film laminate being composed of a carrier film and an optical film having a thin polarizing film, the optical film being laminated on the carrier film via an adhesive layer. In this method, a plurality of slits are formed in the width direction of the optical film laminate with a carrier film, and the slits have a predetermined interval in the longitudinal direction, so that optical film sheets are formed between 2 slits adjacent in the longitudinal direction. The optical film is peeled from the carrier film just before the position where the optical film is bonded to the panel, the front end portion of the optical film in the moving direction is sucked by vacuum suction to be overlapped with the panel fed to the bonding position, and the panel and the optical film are bonded to each other through the adhesive layer.

Description

Method and apparatus for sequentially laminating optical films having polarizing films on rectangular panel

The present application is a divisional application entitled "method and apparatus for sequentially laminating optical films having polarizing films on a rectangular panel", having an application date of 2011, 9/5, and an application number of 201110259770.4.

Technical Field

The present invention relates to a method and apparatus for sequentially laminating optical films having polarizing films on a rectangular panel. In particular, the present invention relates to a method for sequentially laminating optical films having a very thin polarizing film having a thickness of 10 μm or less to a panel.

Background

A method for producing a polarizing film comprising a PVA type resin layer in which molecules of the PVA type resin are oriented in a stretching direction and a dichroic material is adsorbed in the PVA type resin in an oriented state is widely known by subjecting a single layer of a polyvinyl alcohol type resin (hereinafter referred to as "PVA type resin") formed in a film shape to dyeing and stretching. The thickness of the polarizing film obtained by the conventional method using the PVA resin single-layer film is approximately 15 to 35 μm. According to this method, a polarizing film having optical characteristics such as a single-body transmittance of 42% or more and a degree of polarization of 99.95% or more can be obtained, and the polarizing film produced by this method is now used in televisions, mobile phones, portable information terminals, and other optical display devices.

However, since the PVA type resin is hydrophilic and highly hygroscopic, a polarizing film produced using the PVA type resin is sensitive to changes in temperature and humidity, and tends to be easily cracked due to expansion and contraction caused by changes in the surrounding environment. Therefore, in the conventional general polarizing film, an optical film laminate having TAC (triacetyl cellulose) films of 40 to 80 μm as protective films attached to both surfaces thereof is used.

In addition, another problem in the case of using a conventional polarizing film comprising a PVA-based resin layer is that the polarizing film is subjected to stress on an adjacent member joined thereto due to expansion and contraction caused by environmental changes during use, and the adjacent member is deformed such as warp.

Even in an optical film laminate in which TAC (triacetyl cellulose) films are bonded as protective films on both surfaces of a polarizing film, when a polarizing film formed of a single layer is used, since there is a limit to the thinning of the polarizing film, the stretching force cannot be ignored, and it is difficult to completely suppress the influence of stretching, and the optical film laminate including the polarizing film inevitably undergoes a certain degree of stretching. When the optical film laminate including the polarizing film is stretched, the adjacent members are deformed such as warped by stress generated by the stretching. Even if the distortion is very small, the distortion causes display unevenness in the liquid crystal display device. Therefore, in order to reduce the occurrence of such display unevenness, it is necessary to carefully select the material of the member used for the optical film laminate including the polarizing film in designing. In addition, since the shrinkage stress of the polarizing film causes peeling of the optical film laminate from the liquid crystal display panel, it is necessary to use an adhesive having high adhesion in order to bond the optical film laminate to the liquid crystal display panel. However, if the adhesive having high adhesion is used, when an optical defect is found in the polarizing film of the optical film laminate bonded to the liquid crystal display panel in a post-inspection, there is a problem that it is difficult to perform a rework process of peeling the optical film laminate from the liquid crystal display panel and bonding another optical film laminate to the liquid crystal display panel. This is a technical problem of a polarizing film obtained by a conventional method using a film-shaped PVA-based resin single layer.

In view of the above problems, a polarizing film manufacturing method has been desired to replace the conventional polarizing film manufacturing method using a PVA type resin single layer, which cannot be sufficiently thinned. However, the conventional method using a film-shaped PVA based resin single layer has not been able to produce a polarizing film having a thickness of 10 μm or less. The reason is as follows: in the process of producing a polarizing film comprising a film-like PVA-based resin single layer, if the thickness of the PVA-based resin single layer is too small, the PVA-based resin layer may be dissolved and/or broken in the dyeing step and/or the stretching step, and thus a polarizing film having a uniform thickness cannot be formed.

In order to solve the above problems, the following manufacturing method is proposed: a polarizing film, which is much thinner than a polarizing film obtained by a conventional method, is manufactured by coating a PVA type resin layer on a thermoplastic resin substrate, stretching the PVA type resin layer formed on the resin substrate together with the resin substrate, and dyeing the stretched PVA type resin layer. A polarizing film manufacturing method using the thermoplastic resin substrate attracts attention because a polarizing film having a more uniform thickness can be manufactured, as compared with a polarizing film manufacturing method using a PVA-based resin single layer.

For example, japanese patent No. 4279944 (patent document 1) describes a method for producing the following polarizing plate: a polyvinyl alcohol resin layer having a thickness of 6 to 30 [ mu ] m is formed on one surface of a thermoplastic resin film by a coating method, and then stretched to 2 to 5 times or more, and the polyvinyl alcohol resin layer is used as a transparent film element layer, thereby forming a composite film composed of two layers of the thermoplastic resin film layer and the transparent film element layer. The polarizing plate obtained by this method has a two-layer structure of an optically transparent resin film layer and a polarizing element layer, and the thickness of the polarizing element is 2 to 4 μm according to the description of patent document 1.

In the method described in patent document 1, stretching is uniaxial stretching performed under heating, and the stretching magnification is limited to a range of 2 times or more and 5 times or less as described above. Patent document 1 describes the method as follows: the reason why the draw ratio is limited to 5 or less is that it is difficult to stably produce the film by high-power drawing with a draw ratio exceeding 5. With respect to the ambient temperature at the time of stretching, specifically, in the case of using an ethylene-vinyl acetate copolymer as the thermoplastic resin film, 55 ℃; 60 ℃ in the case of using unstretched polypropylene; in the case of using undrawn nylon, it was 70 ℃. The method described in patent document 1 employs uniaxial stretching in a high-temperature gas atmosphere, and as described in patent document 1, the stretching magnification is limited to 5 times or less, and thus an extremely thin polarizing film of 2 to 4 μm obtained by this method cannot satisfy the optical characteristics desired for a polarizing film used in an optical display device such as a liquid crystal television or an optical display device using an organic EL display element.

Jp 2001-343521 a (patent document 2) and jp 2003-43257 a (patent document 3) also describe a method of forming a polarizing film by coating a thermoplastic resin substrate with a PVA-based resin layer and stretching the PVA-based resin layer together with the substrate. In the case where the substrate is an amorphous polyester resin, the methods described in these patent documents are to uniaxially stretch a laminate comprising a thermoplastic resin substrate and a PVA type resin layer applied to the substrate at a temperature of 70 to 120 ℃. Next, the PVA-based resin layer oriented by stretching is dyed to adsorb the dichroic material. Patent document 2 discloses that the uniaxial stretching may be either longitudinal uniaxial stretching or transverse uniaxial stretching, while patent document 3 discloses a method in which transverse uniaxial stretching is performed and the length in the direction perpendicular to the stretching direction is shrunk by a specific amount during or after the transverse uniaxial stretching. In patent documents 2 and 3, the stretch ratio is usually about 4 to 8 times. The thickness of the obtained polarizing film is described as 1 to 1.6. mu.m.

Although patent documents 2 and 3 describe that the draw ratio is usually 4 to 8 times, the drawing method used is a drawing method in a high-temperature gas atmosphere (high-temperature in-air drawing method), and for example, as described in patent document 1, 5 times is the limit of the draw ratio in order to enable stable drawing by such a method. Patent documents 2 and 3 also do not describe any particular method that can achieve a stretching ratio higher than 5 times by a stretching method in a high-temperature gas atmosphere. In fact, if the examples described in patent documents 2 and 3 are read, it is found that patent document 2 only describes a stretching ratio of 5 times and patent document 3 only describes a stretching ratio of 4.5 times. The present inventors have conducted additional experiments on the methods described in patent documents 2 and 3, and have confirmed that the methods described therein cannot perform stretching at a stretching ratio higher than 5. Therefore, it is understood that patent documents 2 and 3 only describe a stretching ratio of 5 times or less. As described in patent document 1, the optical characteristics of the polarizing films obtained in patent documents 2 and 3 still do not satisfy the optical characteristics desired for the polarizing film used in an optical display device such as a liquid crystal television.

U.S. patent specification No. 4659523 (patent document 4) discloses a method for producing a polarizing film, comprising: the PVA-based resin layer coated and formed on the polyester film is uniaxially stretched together with the polyester film. The method described in patent document 4 aims to provide a polyester film, which is a substrate of a PVA type resin layer, with optical characteristics usable together with a polarizing film, and does not provide a polarizing film comprising a PVA type resin layer, which is thin and has excellent optical characteristics. That is, the method described in patent document 4 is merely to improve the optical characteristics of a polyester resin film stretched together with a PVA-based resin layer as a polarizing film. JP-B-8-12296 (patent document 5) also discloses a method for producing a polarizer material having the same object.

The optical film laminate made of the optical film laminate in which TAC films are laminated on both surfaces of a polarizing film is generally used by being laminated on an optical display panel such as a liquid crystal display panel. A continuous bonding apparatus configured by the following method has been proposed: the optical film laminate is bonded to a carrier film via an adhesive layer to form an optical film laminate with a carrier film, and the optical film laminate with a carrier film is continuously fed in the longitudinal direction while being cut into a length corresponding to the size of a corresponding optical display panel, and is sequentially bonded to the optical display panels. For example, japanese patent No. 4361103 (patent document 6), japanese patent No. 4377961 (patent document 7), japanese patent No. 4377964 (patent document 8), japanese patent No. 4503689 (patent document 9), japanese patent No. 4503690 (patent document 10), and japanese patent No. 4503691 (patent document 11) are all described.

The continuous laminating apparatus for an optical film laminate described in these documents includes a slit forming mechanism for forming slits in a width direction perpendicular to a longitudinal direction of an optical film laminate with a carrier film continuously fed, and the distance between the slits in the longitudinal direction corresponds to one of a long-side direction dimension and a short-side direction dimension of an optical display panel to which the optical film laminate is laminated. The notch forming mechanism can form a notch with a depth from a surface opposite to the carrier film to an interface between the carrier film and the adhesive layer in a width direction of the optical film laminate with the carrier film. Such incision formation is called "half cut". By this half-cut, an optical film laminate sheet having a length corresponding to one of the long-side direction dimension and the short-side direction dimension of the optical display panel is formed between 2 slits adjacent in the longitudinal direction of the optical film laminate with a carrier film. In this case, the width of the optical film laminate corresponds to the other of the longitudinal dimension and the short-side dimension of the optical display panel.

The continuous bonding apparatus for an optical film laminate further includes a panel transport mechanism for sequentially transporting the optical display panels to the bonding position, and each of the optical film sheets is transported toward the bonding position and is simultaneously transported with the optical display panels sequentially transported to the bonding position. A carrier film peeling mechanism is provided in front of the bonding position, and the peeling mechanism functions as follows for each optical film sheet: the optical film sheet is peeled from the carrier film in a state where the adhesive layer is left on the optical film sheet side. Then, the optical film laminate sheet from which the carrier film is peeled is sent to the bonding position, and is superimposed on the panel sent to the bonding position. A bonding mechanism such as a bonding roller is provided at the bonding position, and the optical display panel and the optical film laminate sheet fed to the bonding position are bonded to each other with an adhesive layer interposed therebetween.

The carrier film peeling mechanism has a peeling plate (detachable プレート) having an edge portion in a shape capable of folding the carrier film peeled from the optical film laminate sheet into an acute angle. The optical film laminate sheet is directly peeled from the carrier film without changing the traveling direction and is sent to a bonding position.

Documents of the prior art

Patent document

[ patent document 1] Japanese patent No. 4279944 publication

[ patent document 2] Japanese patent application laid-open No. 2001-343521

[ patent document 3] Japanese patent application laid-open No. 2003-43257

[ patent document 4] specification of U.S. Pat. No. 4659523

[ patent document 5] Japanese examined patent publication No. 8-12296

[ patent document 6] Japanese patent No. 4361103 publication

[ patent document 7] Japanese patent No. 4377961

[ patent document 8] Japanese patent No. 4377964

[ patent document 9] Japanese patent No. 4503689

[ patent document 10] Japanese patent No. 4503690 publication

[ patent document 11] Japanese patent No. 4503691 publication

[ patent document 12] Japanese patent application laid-open No. 2002-258269

[ patent document 13] Japanese patent application laid-open No. 2004-078143

[ patent document 14] Japanese patent laid-open No. 2007 & 171892

[ patent document 15] Japanese patent laid-open publication No. 2004-338379

[ non-patent document 1] H.W.Siesler, adv.Polym.Sci.,65,1(1984)

Disclosure of Invention

Problems to be solved by the invention

The thickness of the polarizing film to be practically used at present is about 15 to 35 μm, usually about 30 μm. And TAC films with a thickness of 60-80 μm are respectively bonded to both surfaces of the polarizing film. Further, an optical function film such as a retardation film is laminated on the polarizing film laminate having TAC films laminated on both surfaces thereof, and then a surface protective film is laminated thereon to form an optical film laminate. Therefore, even in a state where the thickness of the adhesive layer for bonding the carrier film is removed, the thickness of the entire optical film laminate is 200 to 270 μm. However, recently, with the reduction in thickness of display devices, it is strongly required to reduce the thickness of the optical film laminate as much as possible.

On the other hand, the present inventors have succeeded in producing a polarizing film having a thickness of 10 μm or less and having optical characteristics required for a polarizing film used together with a liquid crystal display panel or an organic EL display panel. Specifically, the present inventors have succeeded in obtaining a thin polarizing film, which has a thickness of 10 μm or less and has optical properties represented by a cell transmittance T and a polarization degree P that satisfy the properties required for a polarizing film used in an optical display device, and which has been hitherto unavailable, by a method for producing a polarizing film, which comprises: an ester-based thermoplastic resin base material and a PVA-based resin layer coated thereon are integrated, and the base material is stretched by a 2-stage stretching step consisting of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution; and subjecting the PVA-based resin layer to dyeing treatment with a dichroic dye. Under such circumstances, development and research have been continued to form an optical film laminate that is thinner as a whole. When a thin polarizing film developed by the present inventors is used, an optical film laminate having an overall thickness of 170 μm or less can be produced. Further, it is desired to bond such a thin optical film laminate to an optical display panel by using the continuous bonding apparatus described in patent documents 6 to 11.

In the present invention, the "stretching in a gas atmosphere" means stretching in a gas atmosphere without immersion in water or an aqueous solution; the "auxiliary stretching" refers to "stretching in a preceding stage" performed before the 2 nd stage stretching is performed.

However, the present inventors have conducted studies and found that it is difficult to continuously bond such a thin optical film laminate using the conventional apparatus. The reason for this is the thickness of the optical film laminate. As described above, the conventional laminate has a thickness of 200 μm even when it is thin. The laminate having such a thickness has sufficient rigidity, and even after the separation film is peeled by the peeling mechanism, it can be directly sent to the bonding position without changing the traveling direction. However, if the thickness is 170 μm or less, the separation film is peeled from the laminate due to insufficient rigidity of the optical film laminate, and when the laminate is conveyed in the traveling direction, the laminate is bent downward by gravity, and when the laminate is laminated on the optical display panel, problems such as wrinkles and bubbles occur in the laminating unit.

The invention aims to provide a method and a device for sequentially laminating an optical film laminated body, which can solve the problems generated when the thin optical film laminated body is continuously laminated.

Means for solving the problems

One embodiment of the present invention relates to a method for sequentially bonding an optical film laminate to a rectangular panel having a long side and a short side, the method using an optical film laminate with a carrier film, the optical film laminate being composed of an optical film and a carrier film, the optical film including at least a polarizing film having a thickness of 10 μm or less, the optical film being bonded to the carrier film via an adhesive layer, and the adhesive force between the carrier film and the adhesive layer being weaker than that between the optical film and the adhesive layer.

The method comprises the following steps: a plurality of slits are formed in sequence in the width direction of the optical film laminate with the carrier film, the plurality of slits having a distance in the longitudinal direction corresponding to one of the long side dimension and the short side dimension of the optical panel, the slits having a depth from the surface of the optical film on the opposite side of the carrier film to the surface of the carrier film adjacent to the optical film, and an optical film sheet supported by the carrier film is formed between 2 slits adjacent in the longitudinal direction.

In addition, the method further comprises: sequentially conveying the panels to a bonding position; and a step of feeding the optical film laminate with the carrier film, on which the slit is formed, to a bonding position, and sequentially feeding the respective optical film sheets to the bonding position at the same time.

In this method, while the optical film sheet is peeled from the carrier film in a state where the adhesive layer remains on the optical film sheet side immediately before the bonding position, at least the leading end portion of the optical film sheet in the moving direction is held so as to be overlapped with the panel fed to the bonding position, and the panel and the optical film sheet are bonded to each other via the adhesive layer.

In the method of the embodiment of the present invention, it is preferable that the polarizing film is formed on the resin base material by: subjecting a laminate having a polyvinyl alcohol resin layer formed on a continuous strip-shaped thermoplastic resin base material to 2-stage longitudinal uniaxial stretching consisting of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution so that the total stretching ratio is 5 to 8.5 times; and dyeing with 2-color pigments. In this case, the optical film is a laminate in which a polarizing film is formed on a thermoplastic resin substrate.

In the above embodiment of the present invention, the entire thickness of the optical film laminate is preferably 170 μm or less. As the optical film laminate, it is preferable to use one having a width corresponding to the other of the long side dimension and the short side dimension of the panel.

In the method of the present invention, it is preferable that the holding of the optical film in the bonding step is performed by vacuum suction. In this case, the vacuum suction may be performed by making the attaching roller in a structure of a vacuum suction roller that presses and attaches the optical film sheet to the panel; alternatively, the vacuum suction may be performed by a vacuum suction plate provided just in front of the attaching position.

In the method of the present invention, the optical film may be a laminate in which an optical functional film is bonded to a surface of the polarizing film on the side opposite to the carrier film. In addition, as for the optical film, a 2 nd optical functional film may be further provided between the polarizing film and the adhesive layer. The carrier film has a surface in contact with the adhesive layer, the surface having a weaker adhesion to the adhesive layer than the adhesion between the optical film and the adhesive layer.

In the method of the present inventionWhen the monomer transmittance is T and the polarization degree is P, the polarizing film has optical properties satisfying the following conditions: p > - (10)^{0.929T―42.4}-1). times.100 (wherein, T < 42.3), and P.gtoreq.99.9 (wherein, T.gtoreq.42.3), the polarizing film having such optical characteristics is suitable for a liquid crystal display device. Alternatively, when the monomer transmittance is T and the polarization degree is P, the polarizing film has optical characteristics satisfying the following conditions: t.gtoreq.42.5 and P.gtoreq.99.5, and the polarizing film having such optical characteristics is suitable for an organic EL display device.

In the method of the present invention in which the 2-stage stretching is performed, the stretching ratio in the auxiliary stretching in a gas atmosphere is preferably 3.5 times or less. Further, the adsorption of the dichroic substance is preferably performed by the following method: the polyvinyl alcohol resin layer is immersed in a dyeing solution containing iodine in an aqueous solvent in a concentration range of 0.12 to 0.30 wt%.

Another embodiment of the present invention relates to a bonding apparatus for sequentially bonding an optical film to a rectangular panel having a long side and a short side, using an optical film laminate with a carrier film, the optical film laminate being composed of an optical film and a carrier film, the optical film including at least a polarizing film having a thickness of 10 μm or less, the carrier film being bonded to the optical film via an adhesive layer, and the adhesive force between the carrier film and the adhesive layer being weaker than the adhesive force between the optical film and the adhesive layer.

This laminating device includes:

an optical film laminate feeding mechanism for feeding the optical film laminate with the carrier film in the longitudinal direction;

a notch forming mechanism for sequentially forming a plurality of notches in a width direction of the optical film laminate with the carrier film, which is conveyed in a longitudinal direction by the conveying mechanism, the plurality of notches having an interval in the longitudinal direction corresponding to one of a long side dimension and a short side dimension of the optical panel, the notches having a depth from a surface of the optical film on a side opposite to the carrier film to a surface of the carrier film adjacent to the optical film, and forming an optical film sheet supported by the carrier film between 2 notches adjacent in the longitudinal direction;

the panel conveying mechanism is used for sequentially conveying the panels to the laminating position;

a carrier film peeling mechanism that feeds each optical film sheet to the bonding position in synchronization with the panel sequentially fed to the bonding position, and feeds the optical film sheet to overlap the panel fed to the bonding position while peeling the optical film sheet from the carrier film in a state where the adhesive layer remains on one side of the optical film sheet, immediately before the bonding position; and

and a bonding mechanism which is arranged at a bonding position and bonds the panel sent to the bonding position and the optical film through an adhesive layer.

The bonding apparatus of the present invention is provided with a holding mechanism for holding at least a moving direction leading end portion of the optical film sheet after the carrier film is peeled off and feeding the sheet to the bonding mechanism. In this case, the holding means preferably comprises a vacuum suction device. The holding mechanism has the following structure: the bonding roll constituting the bonding mechanism was a vacuum suction roll. Alternatively, the holding mechanism may be constituted by a vacuum suction plate.

In the prior art, it has not been possible to achieve the desired optical properties for use in optical display devices by making the thickness of the polarizing film 10 μm or less.

Here, in the case of a polarizing film used in an optical display device such as a liquid crystal television, for example, the present inventors set the optical properties desired for the polarizing film to the following conditions, where the monomer transmittance is T and the degree of polarization is P:

P＞－(10^{0.929T―42.4}-1) x 100 (wherein T < 42.3), and

p is more than or equal to 99.9 (wherein, T is more than or equal to 42.3).

In addition, unlike the case of a liquid crystal display device, in the case of an organic EL display device, since a general configuration is such that 1 polarizing film is used, optical characteristics required for the polarizing film are different from those required for the polarizing film used in the liquid crystal display device. Therefore, as optical characteristics required for a polarizing film used for an organic EL display device, the present inventors set them as follows: when the monomer transmittance is T and the polarization degree is P, the conditions of T.gtoreq.42.5 and P.gtoreq.99.5 are satisfied.

Since the conventional polarizing film production method using a PVA-based resin film employs stretching in a high-temperature gas atmosphere, there is a limit to the stretching magnification, and if an extremely thin polarizing film having a thickness of 10 μm or less is produced, the desired optical properties of the polarizing film used in the optical display device cannot be obtained. However, by the above-described stretching and dyeing method developed by the present inventors, a polarizing film having a thickness of 10 μm or less and satisfying the above-described conditions in terms of optical properties represented by the monomer transmittance T and the degree of polarization P can be produced. The present invention recognizes the above-described problems encountered in a continuous laminating apparatus for continuously laminating a thin optical film laminate including a polarizing film having the above-described optical characteristics on an optical display panel, and provides a method and an apparatus for solving the problems.

ADVANTAGEOUS EFFECTS OF INVENTION

As is clear from the above description, according to the present invention, there can be obtained a method and an apparatus for sequentially laminating an optical film laminate, which can solve the problem that occurs when an optical film laminate having a smaller overall thickness than that of the conventional optical film laminate is continuously laminated, by using a thin polarizing film having a thickness of 10 μm or less.

As described above, the following cases are not found in the literature describing the prior art: when a laminate comprising a thermoplastic resin substrate and a PVA resin layer formed on the substrate is uniaxially stretched, the stretching ratio is 5 or more.

Hereinafter, representative examples of the method for producing a polarizing film used in the present invention and embodiments of the method and apparatus for continuously laminating an optical film laminate of the present invention will be described in detail with reference to the drawings.

Drawings

Fig. 1 is a graph showing a suitable thickness of a resin base material with respect to a PVA layer thickness, i.e., a polarizing film thickness.

FIG. 2 is a graph showing a comparison of polarizing properties of polarizing films having thicknesses of 3 μm, 8 μm and 10 μm.

FIG. 3 is a graph showing the relationship between the single transmittance P and the degree of polarization T.

Fig. 4 is a graph showing the range of optical performance required for a polarizing film used in an optical display device having an optical display panel.

FIG. 5 is a graph showing theoretical values of polarization performance of polarizing films 1 to 7 based on dichroic ratio.

FIG. 6 is a comparison table for comparing the presence or absence of dissolution of the PVA based resin layer due to the difference in iodine concentration in the dyeing bath.

FIG. 7 is a graph showing the relationship between the iodine concentration in the dyeing bath and the polarization performance of the polarizing film formed of the PVA based resin layer.

Fig. 8 is a graph showing polarization performance of a polarizing film as an example of the present invention.

FIG. 9 is a schematic view of a manufacturing process for manufacturing an optical film laminate, which does not include an insolubilization treatment.

FIG. 10 is a schematic view of a manufacturing process including an insolubilization treatment for manufacturing an optical film laminate.

Fig. 11a is a cross-sectional view showing an example of an organic EL display device using the optical film laminate of the present invention.

Fig. 11b is a cross-sectional view showing another example of an organic EL display device using the optical film laminate of the present invention.

Fig. 12 is a cross-sectional view showing an example of a liquid crystal display device using the optical film laminate of the present invention.

Fig. 13 is a graph comparatively showing polarization properties of polarizing films manufactured by several examples of the present invention.

FIG. 14 is a graph showing polarization performance of a polarization film manufactured by comparing several other examples of the present invention.

Fig. 15 is a graph showing polarization performance of a polarizing film manufactured by an example of the present invention.

Fig. 16 is a graph showing polarization properties of a polarizing film manufactured according to another example of the present invention.

Fig. 17 is a graph showing polarization properties of a polarizing film manufactured according to another example of the present invention.

FIG. 18 is a graph showing the relative relationship between the stretching temperature and the stretching magnification of each of the crystalline PET, amorphous PET and PVA resins.

FIG. 19 is a graph showing changes in crystallization rates of crystalline PET and amorphous PET with changes in temperature between Tg and the melting point Tm.

FIG. 20 is a graph showing the relationship between the stretch ratio and the total stretch ratio of amorphous PET and PVA in a high-temperature gas atmosphere.

FIG. 21 is a graph showing the relative relationship between the stretching temperature and the total stretching magnification of crystalline PET, amorphous PET, or PVA based resin in a high temperature gas atmosphere.

FIG. 22 is a graph showing the relationship between the orientation and crystallinity of PET used as a thermoplastic resin base material and the total draw ratio.

FIG. 23 is a graph showing the relationship between the auxiliary stretching temperature when the auxiliary stretching was performed in a 1.8-fold gas atmosphere and the orientation function of PET after the auxiliary stretching treatment.

FIG. 24 is a graph showing the relationship between the crystallinity of PVA and the orientation function of PVA.

FIG. 25 is a schematic view of a process for producing a polarizing film using a thermoplastic resin base material.

Fig. 26 is a graph showing polarization performance of a polarizing film of a conventional example in which 2-stage stretching is not performed.

FIG. 27 is a list of production conditions of the polarizing film obtained in example in which 2-stage stretching was performed, or an optical film laminate including the polarizing film.

FIG. 28 is a list of production conditions of the polarizing film obtained in example in which 2-stage stretching was performed, or an optical film laminate including the polarizing film.

FIG. 29 is a table comparing values of orientation functions of examples and reference examples 1 to 3 in which 2-stage stretching was performed.

FIG. 30 is a schematic view of a step of manufacturing an optical film laminate roll that can be used in the method of the present invention.

FIG. 31 is a schematic view showing another production process of an optical film laminate roll that can be used in the method of the present invention.

FIG. 32 is a schematic view of a manufacturing process of an optical film laminate roll according to another embodiment.

FIG. 33 is a schematic view of a manufacturing process of an optical film laminate roll according to another embodiment.

Fig. 34 is a schematic view showing a method of bonding an optical film laminate sheet according to an embodiment of the present invention.

FIG. 35 is a schematic view showing a notch forming position in the optical film laminate.

Fig. 36 is a diagram showing a problem encountered in the attaching process of an optical film.

FIG. 37 is a diagram showing an embodiment of the method of the present invention, in which FIG. 37(a) shows an example using a vacuum suction roll and FIG. 37(b) shows an example using a vacuum suction plate.

Fig. 38 is a diagram showing another embodiment of the method of the present invention, in which fig. 38(a), 38(b), and 38(c) show respective steps of the operation, respectively.

FIG. 39 is a schematic view showing another embodiment of the method of the present invention.

Description of the symbols

1 base Material

2 PVA based resin layer

3 polarizing film

4 optical functional film

5 nd 2 nd optical functional film

7 laminate comprising PVA-based resin layer

8 stretched laminate

8' stretch laminate roll

8' insolubilized stretched laminate

9 colored laminate

9' crosslinked colored laminate

10 optical film laminate

10a optical film laminate with adhesive layer

11 optical functional film laminate

20 laminated body manufacturing device

21 coating mechanism

22 drying mechanism

23 surface modification treatment device

Auxiliary stretching treatment device in 30 gas atmosphere

31 stretching mechanism

32 winding device

33 oven

40 dyeing device

41 dyeing liquid

42 dyeing bath

43 continuous drawing device

Device for treating 50 boric acid aqueous solution

51 aqueous solution of boric acid

52 boric acid bath

53 stretching mechanism

60 insolubilization device

Aqueous solution of insolubilized 61-boric acid

70 crosslinking processing device

71 boric acid crosslinked aqueous solution

80 washing device

81 washing liquid

90 drying device

91 winding device

100 laminating/transferring device

101 continuous drawing/bonding device

102 winding/transfer device

(A) Laminate manufacturing Process

(b) Auxiliary stretching process in gas atmosphere

(C) Dyeing process

(D) Drawing process in boric acid aqueous solution

(E) 1 st insolubilization sequence

(F) Comprising the 2 nd insolubilizing crosslinking step

(G) Washing process

(H) Drying step

(I) Bonding/transfer Process

200 laminating device

200b upper side laminating roller

213 vacuum suction roll

500 separation membrane bonding unit

503 separation membrane

680 roll of optical film laminate

630. 650 Defect detecting section

W liquid crystal display panel

670 control device

Detailed Description

[ technical background relating to polarizing film ]

As a background art of the polarizing film, description will be made with respect to optical characteristics characterized by material characteristics of the thermoplastic resin base material used in the present invention and polarizing properties of the polarizing film.

First, general material characteristics of the thermoplastic resin suitable for use in the present invention are summarized.

Thermoplastic resins can be broadly classified into resins in which the high molecules are in a crystalline state in which they are orderly arranged, and resins in which the high molecules are in an amorphous or non-crystalline state in which they have no orderly arrangement or only a very small portion thereof. The former is referred to as a crystalline state, and the latter is referred to as an amorphous or amorphous state. Accordingly, a thermoplastic resin having a property that is not in a crystalline state but can be brought into a crystalline state depending on a change in conditions is referred to as a crystalline resin, and a thermoplastic resin not having the property is referred to as an amorphous resin. On the other hand, a resin which is not in a crystalline state or a resin which does not reach a crystalline state is referred to as an amorphous or non-crystalline resin regardless of whether it is a crystalline resin or an amorphous resin. Here, the term amorphous or amorphous is used separately from the term amorphous which means a property of not forming a crystalline state.

Examples of the crystalline resin include olefin resins including Polyethylene (PE) and polypropylene (PP), and ester resins including polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). One of the characteristics of the crystalline resin is that it has the following properties: generally, the polymers are aligned by heating and/or stretching to promote crystallization. The physical properties of the resin vary depending on the degree of crystallization. On the other hand, crystalline resins such as polypropylene (PP) and polyethylene terephthalate (PET), for example, inhibit crystallization by inhibiting alignment of polymers due to heat treatment and stretching orientation. These polypropylene (PP) and polyethylene terephthalate (PET) in which crystallization is suppressed are called amorphous polypropylene and amorphous polyethylene terephthalate, respectively, and they are collectively called amorphous olefin resin and amorphous ester resin, respectively.

For example, in the case of polypropylene (PP), by making it a random structure having no stereoregularity, amorphous polypropylene (PP) with suppressed crystallization can be produced. In the case of polyethylene terephthalate (PET), for example, an amorphous polyethylene terephthalate (PET) with suppressed crystallization can be produced by copolymerizing a modified group such as isophthalic acid or 1, 4-cyclohexanedimethanol as a polymerization monomer, that is, by copolymerizing a molecule that inhibits crystallization of polyethylene terephthalate (PET).

Next, the optical characteristics of a polarizing film that can be used in a large-sized liquid crystal display element will be summarized.

The optical characteristics of the polarizing film, in fact, refer to the polarizing properties characterized by the degree of polarization P and the monomer transmission T. The polarization degree P of the polarizing film is generally in a dihedral back relationship with the monomer transmittance T. These 2 optical characteristic values can be represented by a T-P curve. In the T-P curve, the more the line obtained by plotting is in the direction of high monomer transmittance and high polarization degree, the more excellent the polarization performance of the polarizing film.

Here, referring to fig. 3 showing a T-P curve, the ideal optical characteristic is a case where T is 50% and P is 100%. As can be seen from fig. 3, if the T value is low, the P value is easy to increase, and the higher the T value is, the more difficult the P value is to increase. In addition, if referring to fig. 4 showing the relationship between the transmittance T and the polarization degree P in the polarization performance of the polarizing film, the single transmittance T and the polarization degree P of the polarizing film in the ranges determined by the regions above the line 1 and the line 2 in fig. 4 are taken as "required performances" necessary for satisfying the liquid crystal display device, the contrast of the display device using the polarizing film is 1000: 1 or more and a maximum luminance of 500cd/m²The above. The required performance is considered to be a performance of optical characteristics required for the performance of a polarizing film of a large liquid crystal display device or the like at present or in the future. The ideal value of the cell transmittance T is T50%, but when light passes through the polarizing film, a phenomenon occurs in which part of the light is reflected at the interface between the polarizing film and the air. In consideration of this reflection phenomenon, the single transmittance T is reduced by an amount corresponding to reflection, and the maximum value of the T value that can be actually realized is about 45 to 46%.

On the other hand, the polarization degree P can be converted into the Contrast Ratio (CR) of the polarizing film. For example, a polarization degree P of 99.95% corresponds to a contrast ratio of the polarizing film of 2000: 1. when the polarizing film was used on both sides of a liquid crystal display panel for a liquid crystal television, the contrast of the display device was 1050: 1. here, the contrast of the display device is lower than that of the polarizing film because depolarization occurs inside the display panel. Depolarization occurs because of the following reasons: when light is transmitted through the inside of the light transmitting element irradiated through the polarizing film on the backlight side, the light is scattered and/or reflected by the action of a pigment, a liquid crystal molecular layer, and a TFT (thin film transistor) in the color filter, and the polarization state of part of the light is changed. The higher the contrast of the polarizing film and the display panel, the more excellent the contrast of the liquid crystal television and the easier the viewing.

The contrast of the polarizing film is defined as a value obtained by dividing the parallel transmittance TP by the perpendicular transmittance Tc. In contrast, the contrast of a display device may be defined as the maximum brightness divided byA value obtained with minimum brightness. The minimum luminance refers to the luminance at the time of full black display. In the case of a liquid crystal television set assumed to be in a normal viewing environment, the required standard is 0.5cd/m²The following minimum luminance. When exceeding this value, color reproducibility is degraded. The maximum luminance refers to luminance at the time of full white display. Assuming that the liquid crystal television is in a normal viewing environment, the maximum brightness is 450-550 cd/m²A display of the range. If the value is less than this, the display becomes dark, and visibility of the liquid crystal television is reduced.

The performance required for a display device for a liquid crystal television using a large-sized display element is as follows: the contrast ratio is 1000: 1 or more and a maximum luminance of 500cd/m²The above. This is considered to be the "required performance" of the display device. Lines 1(T < 42.3%) and 2(T ≧ 42.3%) of FIG. 4 show critical values of polarization properties of the polarizing film necessary for achieving the required properties of the display device. This line was determined by the following simulation based on the combination of the polarizing films on the backlight side and the viewing side shown in fig. 5.

The contrast and the maximum brightness of the display device for a liquid crystal television can be calculated based on the light amount of the light source (backlight), the transmittance of the 2 polarizing films disposed on the backlight side and the viewing side, the transmittance of the liquid crystal display panel, the polarization degrees of the 2 polarizing films on the backlight side and the viewing side, and the depolarization rate of the liquid crystal display panel. Light quantity (10,000 cd/m) of light source using conventional liquid crystal television²) The basic values of the transmittance (13%) and the depolarization rate (0.085%) of the liquid crystal display panel were combined with a plurality of polarizing films having different polarizing properties, and the contrast and the maximum luminance of the liquid crystal television display device in each combination were calculated, whereby the lines 1 and 2 in fig. 4 that satisfy the required properties were derived. That is, when a polarizing film not reaching the line 1 and the line 2 was used, it was found that the contrast of the display device was 1000: 1 or less and a maximum luminance of 500cd/m²The following. The equation used for the calculation is as follows.

Equation (1) is an equation for determining the contrast of the display device, and equation (2) is an equation for determining the maximum luminance of the display device. The formula (3) is a formula for determining the dichroic ratio of the polarizing film.

Formula (1): CRD (Lmax/Lmin)

Formula (2): lmax ═ LB × Tp- (LB/2 × k1B × DP/100)/2 × (k1F-k2F)) × Tcell/100

Formula (3): DR ═ A_k2/A_k1＝log(k2)/log(k1)＝log(Ts/100×(1-P/100)/T_PVA)/log(Ts/100×(1+P/100)/T_PVA)

Wherein the content of the first and second substances,

Lmin＝(LB×Tc+(LB/2×k1B×DP/100)/2×(k1F-k2F))×Tcell/100

Tp＝(k1B×k1F+k2B×k2F)/2×T_PVA

Tc＝(k1B×k2F+k2B×k1F)/2×T_PVA

k1＝Ts/100×(1+P/100)/T_PVA

k2＝Ts/100×(1-P/100)/T_PVA

CRD: contrast ratio of display device

Lmax: maximum brightness of display device

Lmin: minimum brightness of display device

DR: dichroic ratio of polarizing film

Ts: monomer transmittance of polarizing film

P: degree of polarization of polarizing film

k 1: 1 st principal transmittance

k 2: 2 nd principal transmittance

k 1F: k1 of viewing side polarizing film

k 2F: k2 of viewing side polarizing film

k 1B: k1 of backlight side-bias film

k 2B: k2 of backlight side-bias film

A_k1: absorbance of polarizing film in transmission axis direction

A_k2: absorbance of polarizing film in absorption axis direction

LB: light quantity of light source (10000cd/m2)

Tc: vertical transmittance of polarizing film (combination of viewing-side polarizing plate and backlight-side polarizing plate)

Tp: parallel transmittance of polarizing film (combination of viewing-side polarizing plate and backlight-side polarizing plate)

And (Tcell): transmittance of element (13%)

DP: depolarization rate of element (0.085%)

T_PVA: transmittance of PVA film not adsorbing iodine (0.92).

Line 1 of fig. 4 (T < 42.3%) can be derived from the polarizing properties of the polarizing film on the straight line indicated by the polarizing film 3 in fig. 5. In the polarizing film belonging to the polarizing film 3 of fig. 5, when the polarizing film D having the polarizing performance as the point D (open circle) represented by the coordinates (T, P) ═ 42.1%, 99.95% is used on both the backlight side and the viewing side of the display device for liquid crystal television, the required performance can be achieved.

However, even in the polarizing film belonging to the polarizing film 3, when 3 polarizing films a (T: 40.6%, P: 99.998%), B (T: 41.1%, P: 99.994%), or C (T: 41.6%, P: 99.98%) located in a (darker) region where the single transmittance is low are used on both the backlight side and the viewing side, the required performance is not achieved. In the case of using the polarizing film A, B or C as the polarizing film on either the backlight side or the viewing side, in order to achieve the required performance, it is necessary to use a polarizing film having higher monomer transmittance and excellent polarization performance with a degree of polarization of at least 99.9% or more, such as the polarizing film E belonging to the polarizing film 4, the polarizing film F belonging to the polarizing film 5, or the polarizing film G belonging to the polarizing film 7, as the other polarizing film, compared to the polarizing film 3.

The polarization performance of the polarizing films 1 to 7 shown in FIG. 5 can be calculated based on the formula (3). By using the formula (3), the monomer transmittance T and the polarization degree P can be calculated from the Dichroic Ratio (DR) which is an index of the polarization performance of the polarizing film. The dichroic ratio is a value obtained by dividing the absorbance of the polarizing film in the absorption axis direction by the absorbance in the transmission axis direction. The higher the value, the more excellent the polarizing properties. For example, the polarizing film 3 is calculated to be a polarizing film having a polarizing property with a dichroic ratio of about 94. Polarizing films below this value do not achieve the desired properties.

Further, in the case where the polarizing film having a lower polarizing performance than the polarizing film 3, for example, the polarizing film H (41.0%, 99.95%) belonging to the polarizing film 1 or the polarizing film J (42.0%, 99.9%) belonging to the polarizing film 2 is used as the polarizing film on either the backlight side or the viewing side, it is found from the formulas (1) and (2) that in order to achieve the required performance, a polarizing film having a higher polarizing performance than the polarizing film 3, for example, the polarizing film I (43.2%, 99.95%) belonging to the polarizing film 6 or the polarizing film K (42.0%, 99.998%) belonging to the polarizing film 7, must be used as the polarizing film on the other side.

In order to achieve the required performance of the display device for a liquid crystal television, the polarizing performance of the polarizing film on either one of the backlight side and the viewing side must be at least superior to that of the polarizing film 3. Line 1 of FIG. 4 (T < 42.3%) shows its lower limit. On the other hand, line 2(T ≧ 42.3%) of FIG. 4 shows the lower limit value of the degree of polarization P. When a polarizing film having a polarization degree P of 99.9% or less is used as the polarizing film on either the backlight side or the viewing side, the polarizing film on the other side cannot achieve the required performance regardless of the polarizing film having excellent polarizing performance.

As a conclusion, in order to achieve the polarization performance required for a display device for a liquid crystal television using a large-sized display element, it is required as a desired condition that the polarization performance of the polarizing film on either the backlight side or the viewing side is at least in a region exceeding the limit indicated by line 1(T < 42.3%) and line 2(T ≧ 42.3%), more specifically, a polarizing film having a polarization performance superior to that of the polarizing film 3 and a degree of polarization of 99.9% or more is required.

In contrast, in many cases, a polarizing film used for an organic EL display device is mainly used for blocking internal reflection light by forming circularly polarized light in combination with an 1/4-wavelength phase difference film, and in such a case, 1 polarizing film is used. Therefore, unlike the case of a transmissive liquid crystal display device using 2 polarizing films, the polarizing film used in an organic EL display device has different required optical characteristics as described above, and satisfies the conditions represented by t.gtoreq.42.5 and p.gtoreq.99.5 when the monomer transmittance is T and the degree of polarization is P. In fig. 4, required characteristics of a polarizing film used for an organic EL display device are indicated by a chain line.

[ examples relating to the production of polarizing films ]

Examples 1 to 18 are shown as examples of the polarizing film used for the optical film laminate of the present invention. The manufacturing conditions of the polarizing films manufactured in these examples are shown in fig. 27 and 28. In addition, reference examples and comparative examples are shown as comparative examples. Fig. 29 is a table showing the values of the orientation functions of the PET resin base materials for the respective stretched laminates prepared in examples 1 to 18 and reference examples 1 to 3 after the high-temperature stretching in the gas atmosphere of stage 1.

[ example 1]

As the amorphous ester-based thermoplastic resin substrate, a continuous belt-like substrate of isophthalic acid-copolymerized polyethylene terephthalate (hereinafter referred to as "amorphous PET") copolymerized with 6 mol% of isophthalic acid was produced. The glass transition temperature of amorphous PET is 75 ℃. A laminate comprising a continuous belt-shaped amorphous PET base material and a polyvinyl alcohol (hereinafter referred to as "PVA") layer was produced by the following method. The glass transition temperature of PVA was 80 ℃.

An amorphous PET base material having a thickness of 200 μm and a PVA aqueous solution having a concentration of 4 to 5 wt% prepared by dissolving PVA powder having a polymerization degree of 1000 or more and a saponification degree of 99% or more in water are prepared. Next, an aqueous PVA solution was applied to the amorphous PET substrate having a thickness of 200 μm, and the substrate was dried at 50 to 60 ℃ to form a PVA layer having a thickness of 7 μm on the amorphous PET substrate. Hereinafter, the laminate will be referred to as "a laminate having a PVA layer of 7 μm thickness formed on an amorphous PET substrate", a laminate including a PVA layer of 7 μm thickness, or simply "a laminate".

A polarizing film having a thickness of 3 μm was produced by subjecting a laminate including a PVA layer having a thickness of 7 μm to the following steps including a 2-stage stretching step of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution. The laminate including the PVA layer having a thickness of 7 μm was stretched integrally with the amorphous PET substrate by the auxiliary stretching step in a gas atmosphere in the first stage 1 to obtain a stretched laminate including the PVA layer having a thickness of 5 μm. Hereinafter, this will be referred to as "stretched laminate". Specifically, the stretched laminate is produced by the following method: the laminate comprising a PVA layer having a thickness of 7 μm was placed in a stretching apparatus equipped in an oven (the stretching temperature environment was set at 130 ℃ C.), and free-end uniaxial stretching was carried out so that the stretching ratio was 1.8 times. By this stretching treatment, the PVA layer in the stretched laminate was converted into a PVA layer having a thickness of 5 μm in which the PVA molecules were oriented.

Subsequently, a colored laminate in which iodine is adsorbed to a 5 μm thick PVA layer in which PVA molecules are oriented was produced by a dyeing step. Hereinafter, this will be referred to as "colored laminate". Specifically, the colored laminate is produced by the following method: the stretched laminate is immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary time to adjust the monomer transmittance of the finally produced PVA layer constituting the polarizing film to 40 to 44%, thereby adsorbing iodine in the PVA layer contained in the stretched laminate. In this step, the dyeing liquid uses water as a solvent, and has an iodine concentration in the range of 0.12 to 0.30 wt% and a potassium iodide concentration in the range of 0.7 to 2.1 wt%. The ratio of the concentrations of iodine and potassium iodide was 1 to 7.

In addition, to dissolve iodine in water, potassium iodide is required. More specifically, the stretched laminate was immersed in a dyeing solution containing 0.30 wt% of iodine and 2.1 wt% of potassium iodide for 60 seconds to prepare a colored laminate in which iodine was adsorbed in a 5 μm-thick PVA layer in which PVA molecules were oriented. In example 1, the iodine adsorption amount was adjusted by changing the immersion time of the stretched laminate in a dyeing solution having an iodine concentration of 0.30 wt% and a potassium iodide concentration of 2.1 wt%, and the monomer transmittance of the finally produced polarizing film was adjusted to 40 to 44%, whereby various colored laminates having different monomer transmittances and degrees of polarization were produced.

In addition, the colored laminate was further stretched integrally with an amorphous PET substrate by the boric acid aqueous solution stretching step in the 2 nd stage to produce an optical film laminate including a PVA layer constituting a polarizing film having a thickness of 3 μm. Hereinafter, this is referred to as "optical film laminate". Specifically, the optical film laminate is produced by the following method: the colored laminate is placed in a stretching apparatus provided in a processing apparatus set in an aqueous boric acid solution containing boric acid and potassium iodide at a liquid temperature ranging from 60 to 85 ℃ and stretched in a free-end uniaxial stretching to a stretching ratio of 3.3. In more detail, the liquid temperature of the aqueous boric acid solution was 65 ℃. Further, the boric acid content was 4 parts by weight and the potassium iodide content was 5 parts by weight with respect to 100 parts by weight of water.

In this step, the colored laminate having the adjusted iodine adsorption amount is first immersed in an aqueous boric acid solution for 5 to 10 seconds. Then, the colored laminate was passed directly between a plurality of sets of rollers having different rotation speeds, which were stretching devices provided in a processing apparatus, and free end uniaxial stretching was performed for 30 to 90 seconds so that the stretching ratio was 3.3 times. By this stretching treatment, the PVA layer contained in the colored laminate was converted into a PVA layer having a thickness of 3 μm in which the adsorbed iodine was oriented in a single direction and in a higher order in the form of a polyiodide complex. The PVA layer constitutes the polarizing film of the optical film laminate.

As described above, in example 1, the laminate having the PVA layer of 7 μm thickness formed on the amorphous PET base material was first subjected to auxiliary stretching in a gas atmosphere at a stretching temperature of 130 ℃ to prepare a stretched laminate, the stretched laminate was then dyed to prepare a colored laminate, and the colored laminate was further stretched in an aqueous boric acid solution at a stretching temperature of 65 ℃ to prepare an optical film laminate including the PVA layer of 3 μm thickness integrally stretched with the amorphous PET base material at a total stretching ratio of 5.94 times. By such 2-stage stretching, an optical film laminate including a PVA layer having a thickness of 3 μm constituting a polarizing film in which PVA molecules of the PVA layer formed on the amorphous PET substrate are highly oriented and iodine adsorbed by dyeing is unidirectionally highly oriented in the form of a polyiodide complex can be produced.

Although not necessary for producing the optical film laminate, the optical film laminate was taken out from the boric acid aqueous solution in the washing step, and boric acid adhered to the surface of the 3 μm-thick PVA layer formed on the amorphous PET substrate was washed away with a potassium iodide aqueous solution. Then, the washed optical film laminate was dried by a drying step using warm air at 60 ℃. The washing step is a step for eliminating appearance defects such as precipitation of boric acid.

Subsequently, an adhesive was applied to the surface of the 3 μm-thick PVA layer formed on the amorphous PET substrate in the bonding and/or transfer step, and an 80 μm-thick TAC (triacetyl cellulose) film was bonded thereto, and then the amorphous PET substrate was peeled off, so that the 3 μm-thick PVA layer was transferred to the 80 μm-thick TAC (triacetyl cellulose) film.

[ example 2]

Example 2 in the same manner as in example 1, a laminate in which a PVA layer having a thickness of 7 μm was formed on an amorphous PET substrate was first produced, then, the laminate including the PVA layer having a thickness of 7 μm was subjected to auxiliary stretching in a gas atmosphere to produce a stretched laminate which was stretched 1.8 times, and then, the stretched laminate was immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃. Example 2 includes the following crosslinking process different from example 1. In this step, the colored laminate was immersed in a boric acid crosslinking aqueous solution at 40 ℃ for 60 seconds to crosslink the PVA molecules of the iodine-adsorbed PVA layer. The boric acid crosslinking aqueous solution in this step had a boric acid content of 3 parts by weight and a potassium iodide content of 3 parts by weight, based on 100 parts by weight of water.

The crosslinking step of example 2 seeks at least 3 technical effects. No. 1, insolubilization: the PVA layer formed into a thin film contained in the colored laminate is not dissolved in the stretching process in an aqueous boric acid solution as a subsequent step. Color stabilization: iodine that is colored in the PVA layer is not eluted. And 3, node generation: the molecules of the PVA layer are cross-linked to each other, thereby forming a junction.

Next, in example 2, the crosslinked colored laminate was immersed in a 75 ℃ boric acid aqueous solution stretching bath at a stretching temperature of 65 ℃ higher than that of example 1, and stretched in the same manner as in example 1 to a stretching ratio of 3.3, thereby producing an optical film laminate. The washing step, drying step, bonding step and/or transfer step in example 2 were the same as in example 1.

In addition, in order to make the technical effect of the crosslinking step before the stretching step in the aqueous boric acid solution more remarkable, when the uncrosslinked colored laminate of example 1 was immersed in an aqueous boric acid solution stretching bath at a stretching temperature of 70 to 75 ℃, the PVA layer contained in the colored laminate was dissolved in the aqueous boric acid solution stretching bath and could not be stretched.

[ example 3]

Example 3 as in example 1, a laminate in which a PVA layer having a thickness of 7 μm was formed on an amorphous PET substrate was first prepared, and then the laminate including the PVA layer having a thickness of 7 μm was subjected to auxiliary stretching in a gas atmosphere to prepare a stretched laminate having a stretching ratio of 1.8 times. Example 3 includes the following insolubilization step different from example 1. In this step, the stretched laminate is immersed in a boric acid-insoluble aqueous solution at a liquid temperature of 30 ℃ for 30 seconds to insolubilize the PVA layer in which the PVA molecules contained in the stretched laminate are oriented. In the boric acid-insoluble aqueous solution in this step, the boric acid content was 3 parts by weight per 100 parts by weight of water. The insolubilization step of example 3 has a technical effect including at least insolubilization in which the PVA layer contained in the stretched laminate is not dissolved in the dyeing step as a subsequent step.

Next, in example 3, a colored laminate including a PVA layer having iodine adsorbed thereon was prepared by immersing the insolubilized stretched laminate in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃. Then, the colored laminate thus produced was immersed in a 65 ℃ boric acid aqueous solution stretching bath at the same stretching temperature as in example 1, and stretched in the same manner as in example 1 to a stretching ratio of 3.3, thereby producing an optical film laminate. In addition, the washing step, the drying step, the bonding step and/or the transferring step of example 3 are the same as those of example 1.

In order to make the technical conditions and effects of the insolubilization step more remarkable before the dyeing step, the following methods were carried out: first, the non-insolubilized stretched laminate of example 1 was dyed to prepare a colored laminate, and the colored laminate thus prepared was immersed in a stretching bath of an aqueous boric acid solution at a stretching temperature of 70 to 75 ℃. In this case, as described in example 2, the PVA layer contained in the colored laminate was dissolved in the boric acid aqueous solution stretching bath and could not be stretched.

Next, the following method was carried out: the non-insolubilized stretched laminate of example 1 was immersed in a staining solution containing water as a solvent and having an iodine concentration of 0.12 to 0.25 wt% under otherwise unchanged conditions, instead of the staining solution containing iodine at 0.30 wt% in example 1. In this case, the PVA layer contained in the stretched laminate is dissolved in the dyeing bath, and cannot be dyed. However, in the case of using the insolubilized stretched laminate of example 3, even if the iodine concentration of the dyeing liquid is 0.12 to 0.25% by weight, the PVA layer is not dissolved, and the PVA layer can be dyed.

In example 3 in which the PVA layer can be dyed even if the iodine concentration of the dyeing solution is 0.12 to 0.25 wt%, the iodine adsorption amount is adjusted by changing the iodine concentration and potassium iodide concentration of the dyeing solution within the predetermined range shown in example 1 while keeping the immersion time of the stretched laminate in the dyeing solution constant, and the monomer transmittance of the polarizing film finally produced is adjusted to 40 to 44%, thereby producing various colored laminates having different monomer transmittances and degrees of polarization.

[ example 4]

Example 4 an optical film laminate was produced by adding the insolubilization step of example 3 and the crosslinking step of example 2 to the production step of example 1. First, a laminate in which a PVA layer having a thickness of 7 μm was formed on an amorphous PET substrate was prepared, and then, the laminate including the PVA layer having a thickness of 7 μm was subjected to free-end uniaxial stretching by auxiliary stretching in a gas atmosphere so that the stretching ratio was 1.8 times, to prepare a stretched laminate. Example 4 like example 3, the PVA layer in which the PVA molecules contained in the stretched laminate were oriented was insolubilized by an insolubilization step of immersing the stretched laminate in an aqueous solution in which boric acid was insolubilized at a liquid temperature of 30 ℃ for 30 seconds. Example 4a colored laminate including a PVA layer having iodine adsorbed thereon was prepared by immersing a stretched laminate including a PVA layer having undergone insolubilization in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃.

Example 4 the colored laminate thus produced was immersed in a boric acid crosslinking aqueous solution at 40 ℃ for 60 seconds to crosslink the PVA molecules of the PVA layer having iodine adsorbed thereon, as in example 2. Example 4 the crosslinked colored laminate was further immersed in a 75 ℃ boric acid aqueous solution stretching bath at a stretching temperature of 65 ℃ higher than that of example 1 for 5 to 10 seconds, and free-end uniaxial stretching was performed to a stretching ratio of 3.3 times as in example 2, thereby producing an optical film laminate. The washing step, drying step, bonding step and/or transfer step in example 4 were the same as in examples 1 to 3.

In example 4, as in example 3, the PVA layer was not dissolved even when the iodine concentration of the dyeing liquid was 0.12 to 0.25 wt%. In example 4, the amount of iodine adsorbed was adjusted by changing the iodine concentration and potassium iodide concentration of the dyeing solution within the predetermined ranges shown in example 1 while keeping the immersion time of the stretched laminate in the dyeing solution constant, and the monomer transmittance of the finally produced polarizing film was adjusted to 40 to 44%, whereby various colored laminates having different monomer transmittances and degrees of polarization were produced.

As described above, in example 4, a laminate in which a PVA layer having a thickness of 7 μm was formed on an amorphous PET substrate was first produced, and then the laminate including the PVA layer having a thickness of 7 μm was subjected to free-end uniaxial stretching by auxiliary stretching in a gas atmosphere so that the stretching ratio was 1.8 times, thereby producing a stretched laminate. The PVA layer contained in the stretched laminate was insolubilized by immersing the stretched laminate in a boric acid-insolubilized aqueous solution at a liquid temperature of 30 ℃ for 30 seconds. A colored laminate having iodine adsorbed to an insolubilized PVA layer was produced by immersing a stretched laminate including an insolubilized PVA layer in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃. The colored laminate including the iodine-adsorbed PVA layer was immersed in a boric acid crosslinking aqueous solution at 40 ℃ for 60 seconds, thereby causing crosslinking between the PVA molecules of the iodine-adsorbed PVA layer. The colored laminate including the crosslinked PVA layer was immersed in a boric acid aqueous solution stretching solution containing boric acid and potassium iodide at a liquid temperature of 75 ℃ for 5 to 10 seconds, and then stretched in a boric acid aqueous solution to be free-end uniaxially stretched to a stretching ratio of 3.3 times, thereby producing an optical film laminate.

Thus, example 4 can stably produce an optical film laminate including a PVA layer having a thickness of 3 μm constituting a polarizing film, by 2-stage stretching consisting of high-temperature stretching in a gas atmosphere and stretching in an aqueous solution of boric acid, and pre-treatment consisting of insolubilization before dipping in a dyeing bath and crosslinking before stretching in an aqueous solution of boric acid, in which PVA molecules of the PVA layer formed on an amorphous PET substrate are highly oriented and iodine reliably adsorbed on the PVA molecules by dyeing is unidirectionally highly oriented in the form of a polyiodide complex.

[ example 5]

Example 5 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The differences are that: thickness of PVA layer formed on amorphous PET base material. In example 4, a PVA layer having a thickness of 7 μm was used, and the thickness of the PVA layer contained in the final optical film laminate was 3 μm. In contrast, example 5 utilized a PVA layer having a thickness of 12 μm, and the PVA layer contained in the final optical film laminate had a thickness of 5 μm.

[ example 6]

Example 6 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: polymerized monomers for amorphous PET matrix materials. Example 4 used an amorphous PET base material obtained by copolymerizing isophthalic acid and PET. In contrast, example 6 used an amorphous PET substrate obtained by copolymerizing PET and 1, 4-cyclohexanedimethanol as a modifying group.

[ example 7]

Example 7 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratios of the auxiliary stretching in the gas atmosphere and the stretching in the aqueous boric acid solution were respectively changed so that the total stretching ratio was 6 times or a value close to 6 times. In example 4, the stretching ratios of the auxiliary stretching in a gas atmosphere and the stretching in an aqueous boric acid solution were 1.8 times and 3.3 times, respectively. In example 7, the stretching ratios of the auxiliary stretching in a gas atmosphere and the stretching in an aqueous boric acid solution were 1.2 times and 4.9 times, respectively. In addition, the total draw ratio of example 4 was 5.94 times. Whereas example 7 had a total draw ratio of 5.88 times. This is because when stretching in an aqueous boric acid solution, stretching at a stretch ratio of 4.9 or more cannot be performed.

[ example 8]

Example 8 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratios of the auxiliary stretching in the gas atmosphere and the stretching in the boric acid aqueous solution were respectively changed so that the total stretching ratio was 6 times. In example 8, the stretching ratios of the auxiliary stretching in a gas atmosphere and the stretching in an aqueous boric acid solution were 1.5 times and 4.0 times, respectively.

[ example 9]

Example 9 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratios of the auxiliary stretching in the gas atmosphere and the stretching in the boric acid aqueous solution were respectively changed so that the total stretching ratio was 6 times. In example 9, the draw ratios of the auxiliary drawing in a gas atmosphere and the drawing in an aqueous boric acid solution were 2.5 times and 2.4 times, respectively.

[ example 10]

Example 10 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: example 4 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 130 ℃, and example 10 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 95 ℃.

[ example 11]

Example 11 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: example 4 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 130 ℃, and example 11 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 110 ℃.

[ example 12]

Example 12 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: example 4 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 130 ℃, and example 12 set the stretching temperature for the auxiliary stretching in a gas atmosphere to 150 ℃.

[ example 13]

Example 13 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratio of the auxiliary stretching in the gas atmosphere was 1.8 times, and the stretching ratio of the stretching in the boric acid aqueous solution was 2.8 times. Thus, the total stretch ratio of example 13 was about 5 times (to be exact, 5.04 times) as compared with the total stretch ratio of about 6 times (to be exact, 5.94 times) in example 4.

[ example 14]

Example 14 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratio of the auxiliary stretching in the gas atmosphere was 1.8 times, and the stretching ratio of the stretching in the boric acid aqueous solution was 3.1 times. Thus, the total stretch ratio of example 14 was about 5.5 times (more accurately, 5.58 times) as compared with the total stretch ratio of about 6 times (more accurately, 5.94 times) in example 4.

[ example 15]

Example 15 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: the stretching ratio of the auxiliary stretching in the gas atmosphere was 1.8 times, and the stretching ratio of the stretching in the boric acid aqueous solution was 3.6 times. Thus, the total stretch ratio of example 15 was about 6.5 times (more accurately, 6.48 times) as compared with the total stretch ratio of about 6 times (more accurately, 5.94 times) in example 4.

[ example 16]

Example 16 an optical film laminate was produced under the same conditions as in example 4, except for the following differences. The difference lies in that: stretching method by auxiliary stretching in gas atmosphere. In example 4, free-end uniaxial stretching was performed by auxiliary stretching in a gas atmosphere so that the stretching ratio was 1.8 times. In contrast, in example 16, the stretching magnification was made 1.8 times by auxiliary stretching in a fixed-end unidirectional gas atmosphere.

[ example 17]

Example 17 an optical film laminate was produced under the same conditions as in example 16, except for the following differences. At this time, the stretching ratio of the auxiliary stretching in the gas atmosphere was 1.8 times, except that the stretching ratio in the boric acid aqueous solution was 3.9 times. Thus, the total stretch ratio of example 17 was about 7 times (more accurately, 7.02 times) as compared to about 6 times (more accurately, 5.94 times) the total stretch ratio of example 16.

[ example 18]

Example 18 an optical film laminate was produced under the same conditions as in example 16, except for the following differences. The difference lies in that: the stretching ratio of the auxiliary stretching in the gas atmosphere was 1.8 times, and the stretching ratio of the stretching in the aqueous boric acid solution was 4.4 times. Thus, the total stretch ratio of example 18 was about 8 times (more accurately, 7.92 times) as compared to about 6 times (more accurately, 5.94 times) the total stretch ratio of example 16.

Comparative example 1

Comparative example 1a laminate having a PVA layer of 7 μm thickness formed on an amorphous PET substrate was prepared by applying an aqueous PVA solution to an amorphous PET substrate of 200 μm thickness and drying the same under the same conditions as in example 4. Next, the laminate including the PVA layer having a thickness of 7 μm was subjected to free-end uniaxial stretching by high-temperature stretching in a gas atmosphere at a stretching temperature of 130 ℃ to adjust the stretching ratio to 4.0 times, thereby producing a stretched laminate. By this stretching treatment, the PVA layer contained in the stretched laminate was converted into a PVA layer having a thickness of 3.5 μm in which the PVA molecules were oriented.

Subsequently, the stretched laminate was subjected to dyeing treatment to prepare a colored laminate in which iodine was adsorbed in a PVA layer having a thickness of 3.5 μm in which PVA molecules were oriented. Specifically, the colored laminate is produced by the following method: the stretched laminate is immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary period of time, whereby the monomer transmittance of the finally produced PVA layer constituting the polarizing film is 40 to 44%, and iodine is adsorbed in the PVA layer contained in the stretched laminate. In this way, the amount of iodine adsorbed to the PVA layer in which the PVA molecules are oriented was adjusted, and various colored laminates having different monomer transmittances and polarization degrees were produced.

Next, the colored laminate is subjected to a crosslinking treatment. Specifically, the colored laminate was immersed in a boric acid crosslinked aqueous solution containing 3 parts by weight of boric acid and 3 parts by weight of potassium iodide per 100 parts by weight of water at a liquid temperature of 40 ℃ for 60 seconds to crosslink the colored laminate. The crosslinked colored laminate of comparative example 1 corresponds to the optical film laminate of example 4. Therefore, the washing process, the drying process, the bonding and/or the transferring process are the same as those of example 4.

Comparative example 2

Comparative example 2 the stretched laminate of comparative example 1 was stretched under the same conditions as in comparative example 1 to have a stretching ratio of 4.5 times, 5.0 times, or 6.0 times, to prepare a stretched laminate. The comparative table shows the phenomenon occurring in the amorphous PET base material having a thickness of 200 μm and the PVA layer formed on the amorphous PET base material, including comparative examples 1 and 2. From this, it was confirmed that there was a limit of 4.0 times in the draw ratio in the high-temperature drawing in the gas atmosphere at a draw temperature of 130 ℃.

[ technical background relating to stretching ]

Fig. 18 to 22 are drawn based on the experiment. First, fig. 18 is a graph showing the relative relationship between the stretching temperature and the stretching ratio of each of the crystalline PET, the amorphous PET, and the PVA-based resin, based on an experiment, as shown in fig. 18.

In fig. 18, the thick line indicates the change in the stretch ratio of the amorphous PET with the change in the stretching temperature. Amorphous PET has a Tg of about 75 ℃ and cannot be stretched below this temperature. As can be seen from fig. 18, the free end uniaxial stretching at a high temperature in a gas atmosphere can be pulled at a temperature higher than about 110 ℃ by a factor of 7.0 or more. On the other hand, thin lines in fig. 18 indicate changes in the stretch ratio of crystalline PET with changes in the stretching temperature. Crystalline PET has a Tg of about 80 ℃ and cannot be stretched below this temperature.

Next, fig. 19 shows the change in the crystallization rate of each of crystalline PET and amorphous PET with the change in the temperature between Tg and melting point Tm of polyethylene terephthalate (PET). As is clear from FIG. 19, crystalline PET in an amorphous state at about 80 to 110 ℃ rapidly crystallizes at about 120 ℃.

As shown in fig. 18, the upper limit of the stretch ratio of the crystalline PET obtained by the high-temperature free-end uniaxial stretching in a gas atmosphere is 4.5 to 5.5 times. Moreover, the stretching temperature that can be applied is extremely limited, ranging from about 90 ℃ to about 110 ℃.

In FIG. 29, reference examples 1 to 3 are shown as examples of high-temperature free-end uniaxial stretching in a gas atmosphere using crystalline PET. These polarizing films were each a polarizing film having a thickness of 3.3 μm, which was produced by stretching a PVA laminate having a thickness of 7 μm formed on a crystalline PET substrate having a thickness of 200 μm at a high temperature in a gas atmosphere. The stretching temperatures were different from each other, and the stretching temperature in reference example 1 was 110 ℃, the stretching temperature in reference example 2 was 100 ℃ and the stretching temperature in reference example 3 was 90 ℃. Notably the stretch magnification. The limit of the stretch ratio in reference example 1 was 4.0 times, and that in reference examples 2 and 3 was 4.5 times. Since the final laminate itself is broken, stretching treatment higher than these stretching ratios cannot be performed. As a result, it is undeniable that the stretching ratio of the PVA-based resin layer itself formed on the crystalline PET substrate may be affected.

In fig. 18, the broken line in the figure indicates the stretch ratio of the PVA belonging to the PVA-based resin. The PVA resin has a Tg of 75 to 80 ℃ and a single layer of the PVA resin cannot be stretched at a temperature lower than that temperature. As shown in fig. 18, when the free end is uniaxially stretched at a high temperature in a gas atmosphere, the limit of the stretch ratio of the single layer body made of the PVA-based resin is 5.0 times. Thus, the present inventors clarified the following facts: from the relationship between the stretching temperature and the stretching ratio of each of the crystalline PET and the PVA based resin, it is found that the limit of the stretching ratio of the laminate comprising the PVA based resin layer formed on the crystalline PET substrate when the laminate is subjected to the high-temperature free-end uniaxial stretching in a gas atmosphere is 4.0 to 5.0 times within the stretching temperature range of 90 to 110 ℃.

Next, table 1 below shows the case where the laminates of comparative examples 1 and 2, in which the PVA-based resin layer was formed by coating the amorphous PET base material, were subjected to free-end uniaxial stretching at a high temperature in a gas atmosphere. The amorphous PET matrix material is not limited by the stretching temperature. The polarizing film of comparative example 1 was produced by subjecting a laminate comprising a 7 μm-thick PVA-based resin layer formed on a 200 μm-thick amorphous PET substrate to high-temperature free-end uniaxial stretching in a gas atmosphere at a stretching temperature of 130 ℃. The draw ratio in this case was 4.0 times.

Referring to table 1, the polarizing film of comparative example 2 was produced by stretching a PVA-based resin layer having a thickness of 7 μm formed on an amorphous PET substrate having a thickness of 200 μm so as to have stretching ratios of 4.5 times, 5.0 times, and 6.0 times, respectively, in the same manner as in comparative example 1. In any of the comparative examples, as shown in table 1, there was a possibility that the PVA-based resin layer was broken when the stretching ratio was 4.5 times, while the film was broken due to the occurrence of uneven stretching in the plane of the film on the amorphous PET substrate. Thereby confirming that: when the high-temperature stretching was performed in a gas atmosphere at a stretching temperature of 130 ℃, the limit of the stretching ratio of the PVA-based resin layer was 4.0 times.

[ Table 1]

Comparison table

In each of reference examples 1 to 3, the laminate having the PVA type resin layer formed on the crystalline PET substrate was subjected to stretching treatment of 4.0 to 4.5 times, although the stretching temperature was different, to orient the PVA molecules and adsorb iodine in the PVA type resin layer formed into a thin film, thereby producing a colored laminate. Specifically, the stretched laminate is immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary time, so that the monomer transmittance of the finally produced PVA type resin layer constituting the polarizing film is 40 to 44%, whereby iodine is adsorbed in the PVA type resin layer contained in the stretched laminate. Further, various polarizing films having different monomer transmittances T and degrees of polarization P were produced by adjusting the amount of iodine adsorbed in the thinned PVA-based resin layer.

Referring to fig. 26, lines 1 and 2 in fig. 26 are lines that specify optical characteristics required for a polarizing film used in the optical display device of the present invention, and a polarizing film having a relationship between degrees of polarization P and T located above the lines 1 and 2 satisfies the required optical characteristics. In fig. 26, the optical characteristics of the polarizing films of reference examples 1 to 3 are shown in comparison with the lines 1 and 2. As is clear from FIG. 26, none of the polarizing films of reference examples 1 to 3 satisfied the required optical properties. The reason is presumed to be: the PVA molecules are oriented to some extent by stretching the PVA-based resin layer formed on the crystalline PET substrate at a high temperature in a gas atmosphere, but on the other hand, the high temperature stretching in a gas atmosphere promotes the crystallization of the PVA molecules and inhibits the orientation of the amorphous portion.

Therefore, the present inventors developed the polarizing film disclosed in PCT/JP2010/001460 international application and the method of manufacturing the same before the present invention. The method is completed based on the following viewpoints: the plasticizer function of water is focused on that a laminate including a PVA type resin layer formed on a PET substrate can be stretched even at a stretching temperature of Tg or less. In the present invention, an example of a polarizing film produced by this method is referred to as comparative example 3. According to this method, a laminate including a PVA-based resin layer formed on a PET substrate can be stretched at a stretch ratio of 5.0 times.

The present inventors subsequently continued to study, and confirmed that the reason why the limit of the stretch ratio is 5.0 times is because the PET base material is formed of crystalline PET. Since a laminate including a PVA-based resin layer formed on a PET substrate is stretched in an aqueous boric acid solution having Tg or less, it is considered that the stretching action is not greatly affected by whether the PET substrate is crystalline or amorphous, but when amorphous PET is used, it is found that the laminate can be stretched at a stretch ratio of 5.5 times. In this case, when amorphous PET was used as the base material, and the polarizing film production method shown in comparative example 3 was used as well, it is assumed that the reason why the limit of the draw ratio was 5.5 times was that the amorphous PET base material affected the limitation of the draw ratio.

Comparative example 1 various polarizing films having different cell transmittances T and degrees of polarization P were produced. FIG. 26 shows the optical characteristics thereof together with reference examples 1 to 3.

Fig. 20 shows a relationship between a stretching ratio of high-temperature stretching in a gas atmosphere in 2-stage stretching and a total stretching ratio (hereinafter referred to as "total stretching ratio"), which is an idea obtained by the present inventors based on the results of such studies. The horizontal axis represents the draw ratio in drawing in a gas atmosphere at a draw temperature of 130 ℃ by free-end uniaxial drawing. The total draw ratio of the vertical axis indicates: by the 2-stage stretching treatment including high-temperature stretching in a free-end unidirectional gas atmosphere described below, the final stretching is made to be about several times the initial length, with the length before high-temperature stretching in a gas atmosphere, that is, the initial length, being 1. For example, when high-temperature stretching is performed in a gas atmosphere at a stretching temperature of 130 ℃, the stretching ratio is 2 times, and if the subsequent stretching ratio is 3 times, the total stretching ratio is 6 times (2 × 3 — 6). The 2 nd stage stretching step after the high temperature stretching in a gas atmosphere is free end uniaxial stretching in an aqueous boric acid solution at a stretching temperature of 65 ℃ (hereinafter, the stretching treatment while dipping in an aqueous boric acid solution is referred to as "stretching in an aqueous boric acid solution"). By combining these two stretching methods, the results shown in fig. 20 can be obtained.

The solid line in fig. 20 represents the stretch magnification of amorphous PET. In the case where the stretching in the aqueous boric acid solution was directly performed without performing the high-temperature stretching in a gas atmosphere, that is, when the magnification of the high-temperature stretching in a gas atmosphere was 1 time, the limit of the total stretching magnification of the amorphous PET was 5.5 times. When the stretching was performed 5.5 times or more, the amorphous PET was broken. But this value corresponds to the minimum draw ratio of amorphous PET. The larger the stretch ratio at the time of high-temperature stretching in a gas atmosphere, the larger the total stretch ratio of the amorphous PET, and the more than 10 times the stretch ratio.

In contrast, the dotted line in fig. 20 indicates the stretching magnification of the PVA-based resin layer formed on the amorphous PET. In the case where the stretching in the boric acid aqueous solution was directly performed without performing the high-temperature stretching in the gas atmosphere, the total stretching ratio of the PVA-based resin layer was 7 times as large as the maximum ratio. However, the total stretching ratio of the PVA type resin layer decreases as the stretching ratio at the time of high-temperature stretching in a gas atmosphere increases, and the total stretching ratio of the PVA type resin layer is less than 6 times when the stretching ratio at the time of high-temperature stretching in a gas atmosphere is 3 times. When the overall draw ratio of the PVA type resin layer was 6 times, the PVA type resin layer was broken. As is clear from fig. 20, the reason why the laminate including the PVA-based resin layer formed on the amorphous PET substrate cannot be stretched is that the restriction caused by the amorphous PET substrate shifts to the restriction caused by the PVA-based resin layer as the stretching magnification at high temperature in the gas atmosphere increases. That is, the stretching ratio in the PVA gas atmosphere is up to 4 times, and higher stretching ratio cannot be performed. This ratio is assumed to correspond to the total draw ratio of PVA.

Reference is now made to fig. 21. Fig. 21 shows the relationship between the total draw ratio and the drawing temperature in high-temperature drawing in a gas atmosphere when 2-stage drawing of high-temperature drawing in a gas atmosphere and drawing in an aqueous solution of boric acid is performed on crystalline PET, amorphous PET, and PVA-based resin, and therefore fig. 21 is made based on experimental data. Fig. 18 is a graph of crystalline PET, amorphous PET, and PVA-based resin, in which the horizontal axis represents the stretching temperature of high-temperature stretching in a gas atmosphere, and the vertical axis represents the stretching magnification of high-temperature stretching in a gas atmosphere. The difference between fig. 21 and fig. 18 is that: the horizontal axis represents the stretching temperature at the time of high-temperature stretching in a gas atmosphere by 2 times, and the vertical axis represents the total stretching magnification of high-temperature stretching in a gas atmosphere and stretching in an aqueous boric acid solution.

As a method for producing a polarizing film suitable for use in the present invention, a combination of 2-stage stretching steps of high-temperature stretching in a gas atmosphere and stretching in an aqueous boric acid solution is included as follows. Combinations of 2-stage stretching processes are not simply conceivable. As a result of extensive and intensive studies by the present inventors over a long period of time, it was found that the following 2 technical problems can be simultaneously solved by the combination, and this surprising result was achieved. In an attempt to produce a polarizing film by forming a PVA-based resin layer on a thermoplastic resin substrate and stretching and dyeing the PVA-based resin layer, there are 2 technical problems that have not been solved at present.

The 1 st technical problem is that: the stretching ratio and stretching temperature, which have an influence on the improvement of the orientation of the PVA-based resin, are largely limited by the thermoplastic resin base material on which the PVA-based resin is formed.

The 2 nd technical problem is that: even if the problem of limitation of the stretching ratio and stretching temperature can be overcome, in the case of PVA-based resins and PET used as a thermoplastic resin matrix material, crystallization and stretchability of crystalline resins are contradictory physical properties, and thus the stretching of the PVA-based resins is limited by the crystallization of the PVA-based resins.

The 1 st problem is as follows. The limitation in the production of a polarizing film using a thermoplastic resin substrate is caused by the characteristics of the PVA based resin such that the stretching temperature is not less than Tg (about 75 to 80 ℃) of the PVA based resin and the stretching ratio is 4.5 to 5.0 times, as shown in FIG. 18. When crystalline PET is used as the thermoplastic resin base material, the stretching temperature is further limited to 90 to 110 ℃. The polarizing film is produced by forming a thin film of a PVA-based resin layer formed on a thermoplastic resin substrate contained in a laminate by stretching the laminate at a high temperature in a gas atmosphere, and is considered to be inevitably subject to the above-mentioned limitations.

Therefore, the present inventors have focused on the plasticizer function of water and have proposed a method of stretching in an aqueous boric acid solution that can replace high-temperature stretching in a gas atmosphere. However, even when the resin is stretched in an aqueous boric acid solution at a stretching temperature of 60 to 85 ℃, the restriction imposed by the thermoplastic resin matrix material cannot be avoided, that is, when crystalline PET is used, the stretching ratio is limited to 5.0 times, and when amorphous PET is used, the stretching ratio is limited to 5.5 times. This results in limitations in improvement of the PVA molecular orientation and in limitation of optical properties of a polarizing film formed into a thin film. This is the 1 st technical problem.

The solution of the 1 st technical problem can be explained by referring to fig. 22. Fig. 22 is constituted by 2 correlation diagrams. One of the graphs shows the orientation of PET used as a thermoplastic resin base material, and the other graph shows the crystallinity of PET. The horizontal axes of the 2 graphs each represent the total draw ratio of the high-temperature drawing in a gas atmosphere and the drawing in an aqueous boric acid solution. The broken line in fig. 22 indicates the total draw ratio of the drawing in the aqueous boric acid solution alone. The crystallinity of PET, both crystalline and amorphous, increases sharply when the stretch ratio is 4 to 5 times. Therefore, even if the stretching is performed in the boric acid aqueous solution, the limit of the stretching ratio is 5 times or 5.5 times. At this time, the orientation reaches the upper limit, and the tensile tension rises sharply. As a result, the stretching cannot be performed.

In contrast, the solid line of fig. 22 shows the results obtained after the following operations: the free end was uniaxially stretched at a high temperature in a gas atmosphere at a stretching temperature of 110 ℃ to a stretching ratio of 2, and then stretched in an aqueous boric acid solution at a stretching temperature of 65 ℃. Unlike the case where stretching is performed only in an aqueous boric acid solution, the crystallinity of PET is not drastically increased, regardless of whether it is crystalline or amorphous. As a result, the total stretch magnification can be as high as 7 times. At this time, the orientation reaches the upper limit, and the tensile tension rises sharply. As can be seen from fig. 21, this is the result of using high-temperature free-end uniaxial stretching in a gas atmosphere as the stretching method in stage 1. In contrast, as described below, if a so-called fixed-end uniaxial stretching method of restricting shrinkage in a direction perpendicular to the stretching direction at the time of stretching is employed when stretching at a high temperature in a gas atmosphere, the total stretching magnification can be 8.5 times.

In fig. 22, it is confirmed that the relationship between the orientation and the crystallinity of PET used as the thermoplastic resin matrix material is: in both of crystalline PET and amorphous PET, crystallization of PET can be suppressed by auxiliary stretching using high-temperature stretching in a gas atmosphere. Referring to fig. 23 showing the relationship between the auxiliary stretching temperature and the orientation of PET, when crystalline PET is used as the thermoplastic resin base material, the orientation of the crystalline PET after the auxiliary stretching is 0.30 or more at 90 ℃, 0.20 or more at 100 ℃, and 0.10 or more at 110 ℃. If the orientation of PET is 0.10 or more, the stretching tension increases when the 2 nd stage stretching is performed in an aqueous solution of boric acid, and the load on the stretching apparatus is large, which is not preferable as the production condition. Fig. 23 shows that as the thermoplastic resin base material, amorphous PET is preferably used, and further suggests that amorphous PET having an orientation function of 0.10 or less is more preferable, and amorphous PET having an orientation function of 0.05 or less is further preferable.

Fig. 23 is experimental data showing a relationship between a stretching temperature in a gas atmosphere of high-temperature stretching in a gas atmosphere of 1.8 times and an orientation function of PET used as a thermoplastic resin base material. As is clear from fig. 23, PET having an orientation function of 0.10 or less, which enables stretching of a stretched laminate at a high magnification in an aqueous boric acid solution, is amorphous PET. In particular, if the orientation function is 0.05 or less, it is possible to stably perform stretching at a high magnification without causing a large load such as an increase in stretching tension on a stretching apparatus when performing the 2 nd stage stretching in an aqueous solution of boric acid. This can be easily understood from the orientation function values in the examples shown in examples 1 to 18 and reference examples 1 to 3 in fig. 29.

By solving the 1 st problem, the limitation of the stretch ratio due to the PET substrate can be eliminated, and the orientation of the PVA-based resin can be improved by increasing the total stretch ratio. Thus, the optical characteristics of the polarizing film are significantly improved. However, the optical characteristics achieved by the present inventors are not limited to this. This is achieved by solving the 2 nd technical problem.

The 2 nd technical problem is as follows. One of the characteristics of the PVA-based resin and the crystalline resin such as PET as a thermoplastic resin matrix is: generally, the polymer has a property of promoting crystallization by aligning the polymer by heating and stretching orientation. Stretching of the PVA-based resin is limited by crystallization of the PVA-based resin, which is a crystalline resin. It is common knowledge that crystallization and stretchability are contradictory physical properties, and that an increase in crystallization of a PVA type resin hinders orientation of the PVA type resin. This is the 2 nd technical problem. A method for solving this problem will be described with reference to fig. 24. Fig. 24 shows the relationship between the degree of crystallinity of the PVA-based resin and the orientation function of the PVA-based resin calculated based on the 2 experimental results by the solid line and the broken line.

The solid line in fig. 24 shows the relationship between the crystallinity of the PVA-based resin and the orientation of the PVA-based resin as the following samples. First, 6 laminates each including a PVA-based resin layer formed on an amorphous PET substrate were prepared as samples under the same conditions. The prepared 6 laminates each including a PVA-based resin layer were stretched at different stretching temperatures of 80 ℃, 95 ℃, 110 ℃, 130 ℃, 150 ℃ and 170 ℃ by high-temperature stretching in a gas atmosphere to have the same stretching ratio of 1.8 times, thereby producing stretched laminates each including a PVA-based resin layer. The crystallinity of the PVA-based resin layer contained in each of the prepared stretched laminates and the orientation function of the PVA-based resin were measured and analyzed. The measurement method and the analysis method are specifically described below.

The broken line in fig. 24 shows the relationship between the crystallinity of the PVA-based resin and the orientation of the PVA-based resin as a function of the following samples, as indicated by the solid line. First, 6 laminates each including a PVA-based resin layer formed on an amorphous PET substrate were prepared under the same conditions, and thus samples were prepared. The prepared 6 laminates each including a PVA-based resin layer were stretched at the same stretching temperature of 130 ℃ and a high temperature in a gas atmosphere to have different stretching ratios of 1.2 times, 1.5 times, 1.8 times, 2.2 times, 2.5 times, and 3.0 times, respectively, to prepare stretched laminates each including a PVA-based resin layer. The crystallinity of the PVA-based resin layer contained in each of the prepared stretched laminates and the orientation function of the PVA-based resin were measured and analyzed by the methods described below.

As is clear from the solid line in fig. 24, the orientation of the PVA resin layer contained in the stretched laminate is improved as the stretching temperature of the high-temperature stretching in the gas atmosphere is set higher. As is clear from the broken line in fig. 24, when the stretching ratio of the high-temperature stretching in the gas atmosphere is set to a high ratio, the orientation of the PVA-based resin layer contained in the stretched laminate is improved. By previously increasing the orientation of the PVA-based resin before the stretching in the aqueous boric acid solution of the 2 nd stage, that is, by previously increasing the crystallinity of the PVA-based resin, the orientation of the PVA-based resin after the stretching in the aqueous boric acid solution can be increased. Further, it can be confirmed from the T-P curve of the example described later that the orientation of the polyiodide can be improved as a result of improving the orientation of the PVA based resin.

By setting the stretching temperature of the high-temperature stretching in the gas atmosphere of the 1 st stage to a higher temperature or setting the stretching magnification to a higher magnification, the following unexpectedly excellent results were obtained: the orientation of the PVA molecules in the PVA based resin layer produced by stretching in the boric acid aqueous solution of the second stage 2 can be further improved.

The crystallinity (horizontal axis) of the PVA-based resin shown in fig. 24 is referred to. In the coloring step of dyeing by immersing the stretched laminate comprising the PVA type resin layer in an aqueous solution, in order to produce a colored laminate without causing any undesirable phenomenon such as dissolution of the PVA type resin layer, the PVA type resin layer preferably has a crystallinity of at least 27% or more. Thus, the PVA-based resin layer can be dyed without dissolving the PVA-based resin layer. Further, by setting the crystallinity of the PVA-based resin layer to 30% or more, the stretching temperature in the aqueous boric acid solution can be set to a higher temperature. This can realize stable stretching of the colored laminate, and can stably produce a polarizing film.

On the other hand, if the crystallinity of the PVA-based resin layer is 37% or more, the dyeing property is low, and the dyeing concentration must be increased, which may increase the amount of materials used, increase the dyeing time, and decrease the productivity. In addition, if the crystallinity of the PVA-based resin layer is 40% or more, the PVA-based resin layer may be broken during the stretching treatment in the boric acid aqueous solution. Therefore, the crystallinity of the PVA-based resin is preferably 27% or more and 40% or less. More preferably, it is set to 30% or more and 37% or less.

Next, refer to the orientation function (vertical axis) of the PVA-based resin layer of fig. 24. In order to produce a highly functional polarizing film using a resin base material of amorphous PET, it is preferable that the PVA-based resin layer has an orientation function of at least 0.05 or more. Further, if the orientation of the PVA type resin layer is 0.15 or more, the stretching ratio of the colored laminate including the PVA type resin layer in the boric acid aqueous solution can be reduced. This makes it possible to produce a wide polarizing film.

On the other hand, if the orientation function of the PVA-based resin layer is 0.30 or more, the dyeing property is low, and the dyeing concentration must be increased, which may increase the amount of materials used, increase the dyeing time, and decrease the productivity. In addition, if the orientation function of the PVA-based resin layer is 0.35 or more, there may be a problem that the PVA-based resin layer is broken during the stretching treatment in the boric acid aqueous solution. Therefore, the orientation function of the PVA-based resin layer is preferably set to 0.05 or more and 0.35 or less. More preferably, it is set to 0.15 to 0.30.

The solution of the 1 st technical problem is that: in a laminate comprising a PVA based resin layer formed on an amorphous PET base material, preliminary or auxiliary stretching is performed by high-temperature stretching in a gas atmosphere of the 1 st stage in advance, and stretching is performed in an aqueous boric acid solution of the 2 nd stage, whereby the PVA based resin layer can be stretched to a high stretching ratio without being limited by the stretching ratio of the amorphous PET base material, and thus the orientation of PVA can be sufficiently improved.

In addition, the solution of the 2 nd technical problem is that: by preliminarily or supplementarily setting the stretching temperature for the high-temperature stretching in the gas atmosphere of the 1 st stage to a higher temperature or preliminarily or supplementarily setting the stretching magnification to a higher magnification, the orientation of the PVA molecules in the PVA-based resin layer produced by stretching in the boric acid aqueous solution of the 2 nd stage can be further improved, and the unexpected effect can be obtained. In either case, the high-temperature stretching in the gas atmosphere of the 1 st stage may be used as a method for stretching in the gas atmosphere in preparation for or in addition to the stretching in the aqueous boric acid solution of the 2 nd stage. Hereinafter, "high-temperature stretching in a gas atmosphere in the 1 st stage" is referred to as "auxiliary stretching in a gas atmosphere" to distinguish it from the stretching in the boric acid aqueous solution in the 2 nd stage.

The mechanism of solving the 2 nd technical problem by performing the "auxiliary stretching in a gas atmosphere" can be inferred as follows. The auxiliary stretching in the gas atmosphere is performed at a higher temperature or at a higher magnification, and as confirmed in fig. 24, the orientation of the PVA-based resin after the auxiliary stretching in the gas atmosphere is improved. The important reasons for this are presumed to be: the higher the temperature or the higher the magnification, the more the PVA-based resin is stretched while the crystallization thereof is promoted, and therefore, the stretching is performed while the crosslinking points are partially formed. As a result, the orientation of the PVA-based resin is improved. It is presumed that the orientation of the PVA-based resin can be improved by performing auxiliary stretching in a gas atmosphere in advance before stretching in the aqueous boric acid solution, and that boric acid and the PVA-based resin are easily crosslinked when immersed in the aqueous boric acid solution, and are stretched when boric acid forms a knot. As a result, the orientation of the PVA-based resin is also improved after stretching in the boric acid aqueous solution.

As described above, by performing stretching in the 2-stage stretching step consisting of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution, a polarizing film having the following composition can be obtained: the thickness is less than 10 μm, and the optical characteristics represented by the monomer transmittance T and the polarization degree P satisfy the following conditions;

P＞－(10^{0.929T―42.4}-1) x 100 (wherein T < 42.3), and

p is more than or equal to 99.9 (wherein, T is more than or equal to 42.3),

alternatively, when the monomer transmittance is T and the polarization degree is P, the conditions represented by T.gtoreq.42.5 and P.gtoreq.99.5 are satisfied. The dichroic substance may be any one of iodine or a mixture of iodine and an organic dye.

Most importantly, the polarizing film having the optical property value in the range indicated by the above condition, where the monomer transmittance is T and the polarization degree is P, has the performance required for a display device for a liquid crystal television using a large-sized display element or the performance required for an organic EL display device. Specifically, in the case of a liquid crystal television, a liquid crystal television having a contrast ratio of 1000: 1 or more and a maximum luminance of 500cd/m²The above optical display device. This is referred to herein as "required performance". The polarizing film can be used for an optical functional film laminate to be bonded to the viewing side of an organic EL display panel.

In the case of being used for a liquid crystal display panel, the polarizing properties of the polarizing film disposed on either one of the backlight side and the viewing side must be a polarizing film that satisfies at least the optical characteristics. In addition, when a polarizing film having a polarization degree P of 99.9% or less is used as the polarizing film on either the backlight side or the viewing side, it is difficult to achieve the required performance regardless of the polarizing film having excellent polarizing performance used as the other polarizing film.

Next, refer to fig. 1. FIG. 1 shows the results of checking whether the thickness of the amorphous ester-based thermoplastic resin matrix and the coating thickness (polarizing film thickness) of the PVA-based resin layer cause some problems. In fig. 1, the horizontal axis represents the thickness of the thermoplastic resin substrate in μm, and the vertical axis represents the thickness of the PVA-based resin layer applied to the substrate. In the vertical axis, the number in parentheses indicates the thickness of the polarizing film obtained by stretching and dyeing the PVA-based resin layer on the base material. As shown in fig. 1, when the thickness of the substrate is 5 times or less the thickness of the PVA-based resin layer, there is a possibility that a problem may occur in terms of conveyance performance, which may cause a problem. On the other hand, if the thickness of the polarizing film obtained by stretching and dyeing is 10 μm or more, there is a possibility that the polarizing film has a problem in breaking durability.

The thermoplastic resin substrate is preferably an amorphous ester-based material, and examples of the thermoplastic resin substrate include amorphous polyethylene terephthalate including copolymerized polyethylene terephthalate copolymerized with isophthalic acid, copolymerized polyethylene terephthalate copolymerized with cyclohexanedimethanol, and other copolymerized polyethylene terephthalate. The base material may be a transparent resin. The thermoplastic resin base material is described with respect to the case of using an amorphous material, but a crystalline resin material may be used by appropriately setting the stretching conditions.

The dichroic substance used for dyeing the polyvinyl alcohol-based resin is preferably iodine or a mixture of iodine and an organic dye.

In the present invention, an optical functional film may be bonded to a polarizing film formed of a PVA-based resin layer on a thermoplastic resin substrate. The resin substrate is peeled from the polarizing film, and a separation film is laminated on the surface of the polarizing film from which the resin substrate is peeled via an adhesive layer so as to be freely peelable. The separation film is treated so that the adhesion to the pressure-sensitive adhesive layer is weaker than the adhesion between the polarizing film and the pressure-sensitive adhesive layer, whereby the pressure-sensitive adhesive layer can be left on the polarizing film side when the separation film is peeled off. The separation film is useful as a carrier film in the production of a display device using the optical film laminate roll produced by the present invention. Alternatively, only the separation film may be used as a vehicle for providing the adhesive layer on the polarizing film.

In another embodiment of the present invention, an optical functional film laminate can be produced by laminating an optical functional film on a surface of a polarizing film of a thermoplastic resin substrate, for example, an amorphous ester-based thermoplastic resin substrate, on which a PVA-based resin layer is not formed, and laminating a separation film on the optical functional film so as to be peelable with the adhesive layer interposed therebetween. In this case, the optical functional film may be a known optical functional film provided in the display device in order to realize various optical functions. The 1/4 wavelength retardation film described above is used as such an optical functional film. In addition to these, various optical functional films for a viewing angle compensation action are also known. In another embodiment, an optical functional film may be bonded to the surface of the polarizing film opposite to the thermoplastic resin substrate, and a film such as a protective film may be bonded to the optical functional film via an adhesive layer. Furthermore, the thermoplastic base material may be subsequently peeled off, and the separation film may be adhered to the peeled surface of the polarizing film via the adhesive layer. The separation film is peeled off and then subjected to defect inspection, and after the inspection is completed, the peeled separation film or a separately prepared separation film is bonded to the polarizing film via the adhesive layer.

As is clear from fig. 1, the thickness of the thermoplastic resin base material, for example, the amorphous ester-based thermoplastic resin base material is preferably 6 times or more, more preferably 7 times or more the thickness of the PVA-based resin layer formed. If the thickness of the amorphous ester-based thermoplastic resin matrix is 6 times or more the thickness of the PVA-based resin layer, the following problems do not occur: such transportability that the film is broken due to weak strength during transportation in the manufacturing process, and curling properties and transferability of the polarizing film when used as a polarizing film on either the backlight side or the viewing side of a liquid crystal display.

The amorphous ester-based thermoplastic resin matrix is preferably an amorphous polyethylene terephthalate having an orientation function of 0.10 or less and subjected to a high-temperature stretching treatment in a gas atmosphere, including a copolymerized polyethylene terephthalate copolymerized with isophthalic acid, a copolymerized polyethylene terephthalate copolymerized with cyclohexanedimethanol, or other copolymerized polyethylene terephthalates, and may be a transparent resin.

In addition, when the method of the present invention for producing a polarizing film made of a PVA-based resin using a thermoplastic resin substrate is carried out, an insolubilization method for insolubilizing the PVA-based resin is one of important technical problems, and this will be described below.

When a PVA type resin layer formed on a thermoplastic resin substrate is stretched, it is very difficult to adsorb iodine in the PVA type resin layer and to dissolve the PVA type resin layer contained in the stretched intermediate product or the stretched laminate in a dyeing solution. In the process of producing a polarizing film, it is an essential step to adsorb iodine to the PVA type resin layer after the film is made thin. In a normal dyeing step, a plurality of dyeing liquids having different iodine concentrations, wherein the iodine concentration is in the range of 0.12 to 0.25 wt%, are used, and the immersion time is kept constant, thereby adjusting the adsorption amount of iodine in the PVA-based resin layer. Such a normal dyeing treatment causes dissolution of the PVA-based resin layer during the production of the polarizing film, and thus dyeing is impossible. The concentration is a ratio of the total solution amount. The iodine concentration is a ratio of iodine to the total solution amount, and for example, does not include the amount of iodine added as an iodide such as potassium iodide. In the following description, the terms concentration and iodine concentration are used in the same manner.

As is clear from the experimental results shown in fig. 6, the above-described technical problem can be solved by setting the concentration of iodine as the dichroic material to 0.3 wt% or more. Specifically, a laminate including a stretched intermediate product formed of a PVA-based resin layer is dyed with a dyeing solution having a different iodine concentration, and the immersion time is adjusted to produce a colored laminate including a colored intermediate product.

Here, reference is made to fig. 7. Fig. 7 shows the polarization performance of the polarizing film with the iodine concentration adjusted to 0.2 wt%, 0.5 wt%, 1.0 wt%, respectively, without significant difference. In the production process of a colored laminate containing a colored intermediate product, in order to achieve stable and uniform coloring, it is preferable to perform the dyeing with a reduced iodine concentration and a stable dipping time as compared with the dyeing with a short dipping time with an increased iodine concentration.

Referring to fig. 8, 2 different insolubilizations (hereinafter, referred to as "1 st insolubilization and 2 nd insolubilization") performed in the method of the present invention all showed an influence on the optical characteristics of the finally manufactured polarizing film. Fig. 8 shows the results of analysis of the effects of the 1 st insolubilization and the 2 nd insolubilization on the thinned PVA-based resin layer. Fig. 8 shows the optical properties of each of the polarizing films produced in 4 examples 1 to 4, which satisfy the required performance required for a display device for a liquid crystal television using a large-sized display element.

Example 1 is the optical characteristics of the polarizing film produced without the 1 st and 2 nd insolubilization steps. In contrast, example 2 is a polarizing film obtained by performing only the 2 nd insolubilization treatment without performing the 1 st insolubilization step; example 3 is a polarizing film obtained by performing only the 1 st insolubilization treatment without performing the 2 nd insolubilization step; example 4 is a polarizing film obtained by performing the 1 st insolubilization and the 2 nd insolubilization.

In the embodiment of the present invention, a polarizing film satisfying required performance can be manufactured without going through the 1 st insolubilization step and the 2 nd insolubilization step described later. However, as is clear from FIG. 8, the optical properties of the polarizing film of example 1, which was not subjected to the insolubilization treatment, were lower than those of any of the polarizing films of examples 2 to 4. The optical properties of the respective optical property values were compared and increased in the order of example 1 < example 3 < example 2 < example 4. In both of examples 1 and 2, a staining solution having an iodine concentration of 0.3 wt% and a potassium iodide concentration of 2.1 wt% was used. In contrast, in examples 3 and 4, a plurality of dyeing liquids were used in which the iodine concentration was set to 0.12 to 0.25 wt% and the potassium iodide concentration was varied within a range of 0.84 to 1.75 wt%. The group of examples 1 and 3 differs significantly from the group of examples 2 and 4 in that: the former colored intermediate was not subjected to insolubilization, while the latter colored intermediate was subjected to insolubilization. In example 4, not only the colored intermediate but also the stretched intermediate before the coloring treatment was subjected to the insolubilization treatment. The optical characteristics of the polarizing film can be further improved by the 1 st insolubilization and the 2 nd insolubilization.

As is clear from fig. 7, the mechanism for improving the optical characteristics of the polarizing film is not the iodine concentration of the dyeing liquid. But also in the 1 st insolubilization and the 2 nd insolubilization. This finding can be regarded as the 3 rd technical problem in the manufacturing method of the present invention and a solution thereof.

In the embodiment of the present invention, the 1 st insolubilization treatment is carried out so that the PVA-based resin layer made into a thin film contained in the stretched intermediate product (or stretched laminate) is not dissolved, as described below. In contrast, the insolubilization 2 contained in the crosslinking step includes a coloring stabilization process of preventing the iodine colored in the PVA-based resin layer contained in the colored intermediate product (or colored laminate) from being dissolved out during stretching in an aqueous boric acid solution at a liquid temperature of 75 ℃ in the subsequent step; the insolubilization prevents the PVA based resin layer formed into a thin film from being dissolved.

However, if the 2 nd insolubilization step is omitted, the iodine adsorbed in the PVA type resin layer is eluted more in the process of stretching in an aqueous boric acid solution having a liquid temperature of 75 ℃. In order to avoid elution of iodine and dissolution of the PVA-based resin layer, the temperature of the aqueous boric acid solution can be lowered. For example, it is necessary to dip the colored intermediate (or colored laminate) in an aqueous boric acid solution having a liquid temperature reduced to 65 ℃ while stretching. However, as a result, the PVA-based resin layer contained in the colored intermediate (or the colored laminate) cannot be sufficiently softened because the plasticizer function of water cannot be sufficiently exhibited. That is, the colored intermediate product (or the colored laminate) is broken during stretching in an aqueous boric acid solution due to the decrease in the stretching property. It is obvious that the total stretching ratio specified for the PVA-based resin layer cannot be obtained.

Hereinafter, an example of a method for manufacturing a polarizing film used in the present invention will be described with reference to the drawings.

[ outline of production Process ]

Referring to fig. 9, fig. 9 is a schematic view showing a manufacturing process of the optical film laminate 10 including the polarizing film 3 without the insolubilization treatment process. Here, based on the example 1, an outline of a manufacturing method of the optical film laminate 10 including the polarizing film 3 is given.

As the thermoplastic resin substrate, a continuous belt-like substrate of isophthalic acid copolymerized polyethylene terephthalate (hereinafter referred to as "amorphous PET") copolymerized with 6 mol% of isophthalic acid as an amorphous ester was produced. A laminate 7 comprising a continuous belt-shaped amorphous PET substrate 1 having a glass transition temperature of 75 ℃ and a PVA layer 2 having a glass transition temperature of 80 ℃ was produced by the following method.

[ laminate production Process (A) ]

First, an amorphous PET substrate 1 having a thickness of 200 μm and a PVA aqueous solution having a concentration of 4 to 5 wt% prepared by dissolving PVA powder having a polymerization degree of 1000 or more and a saponification degree of 99% or more in water are prepared. Next, in a laminate manufacturing apparatus 20 equipped with a coating apparatus 21, a drying apparatus 22 and a surface modification treatment apparatus 23, a PVA aqueous solution was coated on a 200 μm-thick amorphous PET substrate 1, and the substrate was dried at a temperature of 50 to 60 ℃ to form a 7 μm-thick PVA layer 2 on the amorphous PET substrate 1. The thickness of the PVA layer may be appropriately changed as described later. Hereinafter, the laminate obtained in this manner is referred to as "laminate 7 having a PVA layer formed on an amorphous PET substrate", "laminate 7 including a PVA layer", or simply "laminate 7".

The laminate 7 including the PVA layer was subjected to the following steps including a 2-stage stretching step of auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution, and finally, a polarizing film 3 having a thickness of 3 μm was produced. The polarizing film used in the present invention has a thickness of 10 μm or less, and a polarizing film having an arbitrary thickness of 10 μm or less can be produced by appropriately changing the thickness of the PVA-based resin layer formed on the PET substrate 1.

[ auxiliary stretching Process (B) in gas atmosphere ]

The laminate 7 including the PVA layer 2 having a thickness of 7 μm was integrally stretched with the amorphous PET substrate 1 by the auxiliary stretching step (B) in a gas atmosphere in the first stage 1, to prepare a "stretched laminate 8" including the PVA layer 2 having a thickness of 5 μm. Specifically, in the auxiliary stretching apparatus 30 in a gas atmosphere in which the stretching apparatus 31 was installed in the oven 33, the laminate 7 including the PVA layer 2 having a thickness of 7 μm was passed through the stretching apparatus 31 in the oven 33 in which the stretching temperature environment was set at 130 ℃, and free-end uniaxial stretching was performed so that the stretching ratio was 1.8 times, thereby producing a stretched laminate 8. At this stage, the winding device 32 provided in the oven 30 is used to wind the laminate 8, thereby producing a roll 8' of the stretched laminate 8.

Here, an outline is given with respect to the free end stretching and the fixed end stretching. If a long film is stretched in the conveying direction, the film shrinks in the width direction, which is a direction perpendicular to the stretching direction. Free end stretching refers to a method of performing stretching without inhibiting the shrinkage. The longitudinal uniaxial stretching is a stretching method in which stretching is performed only in the longitudinal direction. Free-end uniaxial stretching is distinguished from fixed-end uniaxial stretching, which is generally performed while suppressing shrinkage occurring in a direction perpendicular to the stretching direction. By this free-end uniaxial stretching treatment, the PVA layer 2 of 7 μm thickness contained in the laminate 7 is converted into the PVA layer 2 of 5 μm thickness in which the PVA molecules are oriented in the stretching direction.

[ dyeing Process (C) ]

Next, in the dyeing step (C), a colored laminate 9 was produced in which iodine as a dichroic material was adsorbed on the PVA layer 2 having a thickness of 5 μm in which the PVA molecules were aligned. Specifically, in the dyeing apparatus 40 equipped with the dyeing bath 42 of the dyeing liquid 41, the stretched laminate 8 continuously drawn out by the continuous drawing apparatus 43 equipped with the roll 8' and installed in the dyeing apparatus 40 at the same time is immersed in the dyeing liquid 41 containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary time to make the monomer transmittance of the PVA layer constituting the polarizing film 3 finally produced 40 to 44%, thereby producing the colored laminate 9 in which iodine is adsorbed on the oriented PVA layer 2 of the stretched laminate 8.

In this step, an aqueous solution having an iodine concentration of 0.30 wt% is used as the dyeing liquid 41 so as not to dissolve the PVA layer 2 contained in the stretched laminate 8. The concentration of potassium iodide in the dyeing solution 41 was adjusted to 2.1 wt% so that iodine was dissolved in water. The ratio of the concentrations of iodine and potassium iodide was 1 to 7. More specifically, the stretched laminate 8 was immersed in a dyeing solution 41 containing 0.30 wt% of iodine and 2.1 wt% of potassium iodide for 60 seconds to prepare a colored laminate 9 in which iodine was adsorbed on a PVA layer 2 having a thickness of 5 μm in which PVA molecules were oriented. In example 1, the iodine adsorption amount was adjusted by changing the immersion time of the stretched laminate 8 in the dyeing solution 41 having an iodine concentration of 0.30 wt% and a potassium iodide concentration of 2.1 wt%, and the monomer transmittance of the polarizing film 3 finally produced was adjusted to 40 to 44%, thereby producing various colored laminates 9 having different monomer transmittances and degrees of polarization.

[ elongation step (D) in an aqueous boric acid solution ]

The colored laminate 9 including the iodine-oriented PVA layer 2 was further stretched by the boric acid aqueous solution stretching step in the 2 nd stage, thereby producing an optical film laminate 10 including a PVA layer having a thickness of 3 μm in which iodine was oriented and constituting the polarizing film 3. Specifically, in the apparatus 50 for treating by stretching in an aqueous boric acid solution, which comprises a boric acid bath 52 containing an aqueous boric acid solution 51 and a stretching apparatus 53, the colored laminate 9 continuously drawn out by the dyeing apparatus 40 was immersed in the aqueous boric acid solution 51 containing boric acid and potassium iodide and having a liquid temperature of a stretching temperature environment of 65 ℃, and then passed through the stretching apparatus 53 provided in the apparatus 50 for treating in an aqueous boric acid solution to have a free end uniaxial stretching ratio of 3.3 times, thereby producing the optical film laminate 10.

More specifically, the boric acid aqueous solution 51 was adjusted to contain 4 parts by weight of boric acid per 100 parts by weight of water and 5 parts by weight of potassium iodide per 100 parts by weight of water. In this step, the colored laminate 9 having the adjusted iodine adsorption amount is first immersed in the boric acid aqueous solution 51 for 5 to 10 seconds. Then, the colored laminate 9 was passed directly between a plurality of sets of rollers having different rotation speeds of the stretching device 53 as the treatment device 50 in the aqueous boric acid solution, and free end uniaxial stretching was performed for 30 to 90 seconds to adjust the stretching ratio to 3.3 times. By this stretching treatment, the PVA layer contained in the colored laminate 9 is converted into a PVA layer having a thickness of 3 μm in which the adsorbed iodine is oriented in a single direction and in a higher order in the form of a polyiodide complex. The PVA layer constitutes the polarizing film 3 of the optical film laminate 10.

As described above, in example 1, the laminate 7 having the PVA layer 2 of 7 μm thickness formed on the amorphous PET substrate 1 was subjected to auxiliary stretching in a gas atmosphere at a stretching temperature of 130 ℃ to prepare a stretched laminate 8, the stretched laminate 8 was then dyed to prepare a colored laminate 9, and the colored laminate 9 was further stretched in an aqueous boric acid solution at a stretching temperature of 65 ℃ to adjust the total stretching ratio to 5.94 times, thereby preparing the optical film laminate 10 including the PVA layer of 3 μm thickness integrally stretched with the amorphous PET substrate. By such 2-stage stretching, an optical film laminate 10 including a PVA layer having a thickness of 3 μm constituting a polarizing film 3 can be produced, in which PVA layer 2 formed on an amorphous PET substrate 1 as the polarizing film 3 has PVA molecules oriented in a high order and iodine adsorbed by dyeing is oriented in a unidirectional high order as a polyiodide complex. The optical film laminate 10 is preferably completed by the subsequent steps of washing, drying, and transferring. The details of the washing step (G), the drying step (H), and the transfer step (I) are described together with the production steps based on example 4 in which an insolubilization treatment step is combined.

[ outline of other production Processes ]

Referring to fig. 10, fig. 10 is a schematic diagram of a manufacturing process of an optical film laminate 10 including a polarizing film 3 having an insolubilization process. Here, a method for manufacturing the optical film laminate 10 including the polarizing film 3 is outlined based on example 4. As can be seen from fig. 10, the production method according to example 4 is assumed to be a production process in which the following steps are combined in the production process according to example 1: a first insolubilization step before the dyeing step, and a crosslinking step including a second insolubilization step before the stretching step in an aqueous boric acid solution. The laminate production step (a), the auxiliary stretching step (B) in a gas atmosphere, the dyeing step (C), and the stretching step in an aqueous boric acid solution (D) combined in this step were the same as those of the production step of example 1, except that the liquid temperature of the aqueous boric acid solution used in the stretching step in an aqueous boric acid solution was different. Therefore, the explanation of this part is omitted, and the explanation will be mainly given for the 1 st insolubilization step before the dyeing step and the crosslinking step including the 2 nd insolubilization before the stretching step in the boric acid aqueous solution.

[ No. 1 insolubilizing step (E) ]

The 1 st insolubilization step is an insolubilization step (E) before the dyeing step (C). In the same manner as in the production process of example 1, in the laminate production process (a), a laminate 7 in which a PVA layer 2 having a thickness of 7 μm was formed on an amorphous PET substrate 1 was produced, and then, in the auxiliary stretching process (B) in a gas atmosphere, the laminate 7 including the PVA layer 2 having a thickness of 7 μm was subjected to auxiliary stretching in a gas atmosphere to produce a stretched laminate 8 including the PVA layer 2 having a thickness of 5 μm. Next, in the insolubilizing step (E) 1, the insolubilizing treatment is performed on the stretched laminate 8 taken out by the continuous take-out apparatus 43 equipped with the roll 8', and an insolubilized stretched laminate 8 ″ is produced. Of course, the insolubilized stretched laminate 8 ″ in this step includes the insolubilized PVA layer 2. Hereinafter, this will be referred to as "insolubilized stretched laminate 8".

Specifically, in the insolubilization apparatus 60 containing the boric acid-insolubilized aqueous solution 61, the stretched laminate 8 was immersed in the boric acid-insolubilized aqueous solution 61 at a liquid temperature of 30 ℃ for 30 seconds. The boric acid-insoluble aqueous solution 61 used in this step contains 3 parts by weight of boric acid (hereinafter referred to as "boric acid-insoluble aqueous solution") per 100 parts by weight of water. This step is intended to perform an insolubilization treatment for preventing the PVA layer having a thickness of 5 μm contained in the stretched laminate 8 from being dissolved at least in the dyeing step (C) to be performed immediately thereafter.

After the insolubilization treatment, the stretched laminate 8 is sent to the dyeing step (C). In the dyeing step (C), a plurality of dyeing liquids with iodine concentrations varying from 0.12 to 0.25 wt% were prepared, unlike in the case of example 1. By using these dyeing solutions and keeping the immersion time of the insolubilized stretched laminate 8 ″ in the dyeing solution constant, the iodine adsorption amount was adjusted so that the monomer transmittance of the finally produced polarizing film was 40 to 44%, and various colored laminates 9 having different monomer transmittances and degrees of polarization were produced. Even when the laminate is immersed in a dyeing solution containing iodine at a concentration of 0.12 to 0.25 wt%, the PVA layer contained in the insolubilized stretched laminate 8' is not dissolved.

[ crosslinking step (F) including No. 2 insolubilization ]

For the following purpose, the crosslinking step (F) described below can be said to include the 2 nd insolubilization step. The crosslinking procedure achieves the following effects: insolubilizing the PVA layer contained in the colored laminate 9 so as not to dissolve in the stretching step (D) in an aqueous boric acid solution as a subsequent step; stabilization of coloring and prevention of elution of iodine that is colored on the PVA layer; no. 3, generation of knots, that is, knots by cross-linking between molecules of the PVA layer, and No. 2 insolubilization can achieve the effects of No. 1 and No. 2.

The crosslinking step (F) is performed as a step before the stretching step (D) in the boric acid aqueous solution. The colored laminate 9 'produced in the dyeing step (C) is crosslinked to produce a crosslinked colored laminate 9'. The crosslinked colored laminate 9' comprises a crosslinked PVA layer 2. Specifically, in the crosslinking treatment apparatus 70 containing an aqueous solution (hereinafter referred to as "boric acid crosslinked aqueous solution") 71 containing boric acid and potassium iodide, the colored laminate 9 was immersed in the boric acid crosslinked aqueous solution 71 at 40 ℃ for 60 seconds, and the PVA molecules of the PVA layer having iodine adsorbed thereon were crosslinked, thereby producing a crosslinked colored laminate 9'. The boric acid crosslinking aqueous solution used in this step contains 3 parts by weight of boric acid and 3 parts by weight of potassium iodide per 100 parts by weight of water.

In the boric acid aqueous solution stretching step (D), the crosslinked colored laminate 9' is immersed in a 75 ℃ boric acid aqueous solution, and the free end uniaxial stretching is performed to adjust the stretching ratio to 3.3 times, thereby producing the optical film laminate 10. By this stretching treatment, the PVA layer 2 containing iodine adsorbed in the colored laminate 9' is converted into the PVA layer 2 having a thickness of 3 μm in which the adsorbed iodine is oriented in a single direction in a higher order in the form of a polyiodide complex. The PVA layer constitutes the polarizing film 3 of the optical film laminate 10.

In example 4, first, a laminate 7 in which a PVA layer 2 having a thickness of 7 μm was formed on an amorphous PET substrate 1 was produced, and then, the laminate 7 was uniaxially stretched at the free end by auxiliary stretching in a gas atmosphere at a stretching temperature of 130 ℃ to have a stretching ratio of 1.8 times, thereby producing a stretched laminate 8. The thus-produced stretched laminate 8 was immersed in a boric acid-insoluble aqueous solution 61 at a liquid temperature of 30 ℃ for 30 seconds, thereby insolubilizing the PVA layer contained in the stretched laminate. The resulting laminate was an insolubilized stretched laminate 8 ″. The insolubilized stretched laminate 8 ″ was immersed in a staining solution containing iodine and potassium iodide at a liquid temperature of 30 ℃, thereby producing a colored laminate 9 in which iodine was adsorbed in the insolubilized PVA layer. The colored laminate 9 including the PVA layer having iodine adsorbed thereon was immersed in the boric acid crosslinking aqueous solution 71 at 40 ℃ for 60 seconds to crosslink the PVA molecules of the PVA layer having iodine adsorbed thereon. A crosslinked colored laminate 9' was produced. The crosslinked colored laminate 9' was immersed in a boric acid aqueous solution stretching bath 51 containing boric acid and potassium iodide at a liquid temperature of 75 ℃ for 5 to 10 seconds, and then stretched in a boric acid aqueous solution to be uniaxially stretched at the free end to a stretching ratio of 3.3 times, thereby producing an optical film laminate 10.

As described above, in example 4, the optical film laminate 10 including the PVA layer having a thickness of 3 μm constituting the polarizing film in which the PVA molecules in the PVA layer 2 formed on the amorphous PET substrate 1 are highly oriented and iodine surely adsorbed to the PVA molecules by dyeing is unidirectionally highly oriented in the form of the polyiodide complex can be stably manufactured by the 2-stage stretching consisting of the high-temperature stretching in the gas atmosphere and the stretching in the aqueous boric acid solution, and the pretreatment consisting of the insolubilization before the immersion in the dyeing bath and the crosslinking before the stretching in the aqueous boric acid solution.

[ washing step (G) ]

In the stretching step (D) in an aqueous boric acid solution, the colored laminate 9 or the crosslinked colored laminate 9' of example 1 or 4 was subjected to a stretching treatment, and then taken out from the aqueous boric acid solution 51. The optical film laminate 10 including the polarizing film 3 taken out is preferably directly sent to the washing step (G). The washing step (G) is intended to wash away unnecessary residues adhering to the surface of the polarizing film 3. The washing step (G) may be omitted, and the optical film laminate 10 including the polarizing film 3 taken out may be directly sent to the drying step (H). However, if the washing treatment is insufficient, boric acid may be precipitated from the polarizing film 3 after the optical film laminate 10 is dried. Specifically, the optical film laminate 10 is sent to a washing apparatus 80, and immersed in a washing liquid 81 containing potassium iodide at a liquid temperature of 30 ℃ for 1 to 10 seconds, so that the PVA in the polarizing film 3 is not dissolved. The concentration of potassium iodide in the washing liquid 81 is about 0.5 to 10% by weight.

[ drying Process (H) ]

The washed optical film laminate 10 is sent to the drying step (H) and dried. Next, the dried optical film laminate 10 is wound into a continuous strip-shaped optical film laminate 10 by a winding device 91 provided in the drying device 90 at the same time, and a roll of the optical film laminate 10 including the thin high-performance polarizing film 3 is manufactured. As the drying step (H), any suitable method can be used, for example, natural drying, air-blast drying, and heat drying. In both examples 1 and 4, the drying was performed for 240 seconds with warm air at 60 ℃ in the drying device 90 of the oven.

[ laminating/transfer Process (I) ]

As described above, the present invention provides a method for manufacturing an optical film laminate roll, in which a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic material is oriented and which is stretched by a 2-stage stretching process including auxiliary stretching in a gas atmosphere and stretching in an aqueous boric acid solution is used, and optical characteristics of the polarizing film satisfy the above-described desired conditions.

In order to form this optical film laminate, an optical film laminate 10 having a thickness of 10 μm or less, for example, including a polarizing film 3 having a thickness of 3 μm manufactured in the above-described examples, which is formed on a thermoplastic resin base material such as an amorphous PET base material, is subjected to defect inspection, and then wound into a roll to form an optical film laminate roll. The optical film laminate roll formed by the method of the present invention is used in, for example, a laminating/transferring step (I) shown in fig. 10. In the bonding/transfer step (I), the optical film laminate 10 is continuously taken out from a roll, and the bonding process and the transfer process described below are simultaneously performed on the optical film laminate 10 continuously taken out from the roll.

The thickness of the polarizing film 3 to be produced by the thinning by stretching is 10 μm or less, and is usually only about 2 to 5 μm. Such a thin polarizing film 3 is difficult to handle as a single body. Therefore, the polarizing film 3 is processed as an optical film laminate 10 in a state where the thermoplastic substrate on which the polarizing film is formed, for example, the amorphous PET substrate is directly left, or is processed as an optical functional film laminate 11 by being laminated and transferred on another optical functional film 4.

In the laminating/transferring step (I) shown in fig. 9 and 10, the polarizing film 3 contained in the continuous belt-shaped optical film laminate 10 is laminated to the separately prepared optical functional film 4 and wound, and in this winding step, the amorphous PET base material is peeled off while the polarizing film 3 is transferred to the optical functional film 4, thereby producing the optical functional film laminate 11. Specifically, the optical film laminate 10 is continuously drawn from a roll by a continuous drawing/laminating apparatus 101 included in the laminating/transferring apparatus 100, the polarizing film 3 of the continuously drawn optical film laminate 10 is transferred to the optical functional film 4 by a winding/transferring apparatus 102, and the polarizing film 3 is peeled from the substrate 1 in the process to produce the optical functional film laminate 11.

In the drying step (H), the optical film laminate 10 wound in a roll by the winding device 91 or the optical functional film laminate 11 produced in the bonding/transfer step (I) may be formed in various forms.

[ optical characteristics of polarizing films obtained under various production conditions ]

(1) Improvement of optical characteristics of polarizing film by insolubilization (examples 1 to 4)

As described above with reference to fig. 8, the polarizing films produced in examples 1 to 4 overcome the above-described problems, and all of these optical characteristics satisfy the required performance required for an optical display device for a liquid crystal television using a large-sized display element. As shown in FIG. 8, the optical properties of the polarizing film of example 1, which was not subjected to the insolubilization treatment, were lower than those of the polarizing films of examples 2 to 4, which were subjected to the 1 st insolubilization treatment and/or the 2 nd insolubilization treatment. The optical properties of the samples were compared, and the optical properties were increased in the order of (example 1) < (example 3 in which only the 1 st insolubilization treatment was performed) < (example 2 in which only the 2 nd insolubilization treatment was performed) < (example 4 in which the 1 st insolubilization treatment and the 2 nd insolubilization treatment were performed). The polarizing film produced by the production method having the 1 st insolubilization step and/or the 2 nd insolubilization step in addition to the production step of the optical film laminate 10 including the polarizing film 3 can be significantly improved in optical characteristics.

(2) Influence on optical characteristics of the polarizing film due to the thickness of the PVA based resin layer (example 5)

In example 4, a PVA layer having a thickness of 7 μm was stretched to form a polarizing film having a thickness of 3 μm. In contrast, example 5 first formed a PVA layer having a thickness of 12 μm, and stretched to form a polarizing film having a thickness of 5 μm. In addition, a polarizing film was produced under the same conditions.

(3) Effect of the amorphous PET base Material on the optical Properties of polarizing film (example 6)

In example 4, an amorphous PET base material obtained by copolymerizing isophthalic acid and PET was used, and in example 6, an amorphous PET base material obtained by copolymerizing PET and 1, 4-cyclohexanedimethanol, which is a modifying group, was used. In example 6, except for this point, a polarizing film was produced under the same conditions as in example 4.

Referring to fig. 13, it was found that there was no significant difference in the optical characteristics of the polarizing films manufactured by the methods based on examples 4 to 6. This is considered to indicate that the thickness of the PVA-based resin layer and the kind of the amorphous ester-based thermoplastic resin do not significantly affect the optical characteristics of the obtained polarizing film.

(4) Improvement in optical characteristics of polarizing film due to auxiliary stretching magnification in gas atmosphere (examples 7 to 9)

In example 4, the stretching ratios of the auxiliary stretching in the gas atmosphere of the 1 st stage and the stretching in the boric acid aqueous solution of the 2 nd stage were 1.8 times and 3.3 times, respectively, and in examples 7 to 9, the stretching ratios were 1.2 times and 4.9 times, 1.5 times and 4.0, 2.5 times and 2.4 times, respectively. In these examples, a polarizing film was produced under the same conditions as in example 4 except for this point. For example, stretching in an aqueous boric acid solution is performed at a stretching temperature of 130 ℃ in an auxiliary stretching in a gas atmosphere and a liquid temperature of 75 ℃. The total stretch ratio of examples 8 and 9 was 6.0 times, which corresponds to 5.94 times of the total stretch ratio when the auxiliary stretch ratio in the gas atmosphere of example 4 was 1.8 times. However, the limit of the total stretch ratio of example 7 is relatively 5.88 times. This is because the stretching ratio cannot be set to 4.9 times or more when stretching is performed in an aqueous boric acid solution. This is presumed to be the influence of the amorphous PET on the stretching magnification mentioned in the correlation between the auxiliary stretching magnification and the total stretching magnification in the gas atmosphere of the stage 1 described with fig. 20.

Referring to fig. 14, as in the case of example 4, the polarizing films of examples 7 to 9 all overcome the technical problems associated with the production of polarizing films having a thickness of 10 μm or less and have optical characteristics satisfying the required performance required for optical display devices. The optical properties of each were compared, and the optical properties were increased in the order of example 7 < example 8 < example 4 < example 9. This indicates that: when the stretching ratio of the auxiliary stretching in the gas atmosphere of the 1 st stage is set in the range of 1.2 to 2.5 times, the optical properties can be improved to the same extent as those of the polarizing film having a high stretching ratio of the auxiliary stretching in the gas atmosphere of the 1 st stage when the final total stretching ratio obtained by the stretching in the boric acid aqueous solution of the 2 nd stage is set to the same extent. In the process for producing the optical film laminate 10 including the polarizing film 3, the auxiliary stretching in the gas atmosphere of the 1 st stage is set to a high stretching magnification, whereby the optical characteristics of each of the produced polarizing film or the optical film laminate including the polarizing film can be remarkably improved.

(5) Improvement in optical characteristics of polarizing film due to auxiliary stretching temperature in gas atmosphere (examples 10 to 12)

In example 4, the auxiliary stretching temperature in the gas atmosphere was set to 130 ℃, and in examples 10 to 12, the auxiliary stretching temperatures in the gas atmosphere were set to 95 ℃, 110 ℃ and 150 ℃. Are all temperatures above the glass transition temperature Tg of PVA. In these examples, a polarizing film was produced under the same conditions as in example 4 except for this point, and the production process included, for example, setting the auxiliary stretching ratio in a gas atmosphere to 1.8 times and the stretching ratio in an aqueous boric acid solution to 3.3 times. The auxiliary stretching temperature in the gas atmosphere of example 4 was 130 ℃. These examples, including example 4, were produced under exactly the same conditions except for the difference in the stretching temperatures of 95 ℃, 110 ℃, 130 ℃ and 150 ℃.

Referring to fig. 15, the polarizing films manufactured in examples 4 and 10 to 12 all overcome the technical problems associated with the manufacture of polarizing films having a thickness of 10 μm or less and have optical characteristics satisfying the required performance required for optical display devices. The optical properties of each were compared, and the optical properties were increased in the order of example 10 < example 11 < example 4 < example 12. This indicates that: when the auxiliary stretching temperature in the gas atmosphere of the 1 st stage is higher than the glass transition temperature and the temperature environment is set so as to be increased from 95 ℃ to 150 ℃ in this order, the optical properties of the final total stretching ratio obtained by stretching in the boric acid aqueous solution of the 2 nd stage are improved to such an extent that the final total stretching ratio is the same as that of the polarizing film set to the high stretching ratio in the auxiliary stretching in the gas atmosphere of the 1 st stage. In the process for producing the optical film laminate 10 including the polarizing film 3, the auxiliary stretching temperature in the gas atmosphere of the 1 st stage is set to a higher temperature, whereby the optical properties of each of the produced polarizing film and the optical film laminate including the polarizing film can be remarkably improved.

(6) Improvement in optical characteristics of polarizing film due to Total draw ratio (examples 13 to 15)

In example 4, the auxiliary stretching ratio in the gas atmosphere of the 1 st stage was set to 1.8 times, and the stretching ratio in the boric acid aqueous solution of the 2 nd stage was set to 3.3 times. In examples 13 to 15, the draw ratios in the aqueous boric acid solution of the 2 nd stage were set to 2.1 times, 3.1 times, and 3.6 times, respectively. This means that the total draw ratios in examples 13 to 15 were set to 5.04 times (about 5 times), 5.58 times (about 5.5 times), and 6.48 times (about 6.5 times). The total draw ratio of example 4 was 5.94 times (about 6 times). The production conditions of these examples including example 4 were completely the same except that the total draw ratio was different from 5 times, 5.5 times, 6.0 times, and 6.5 times.

Referring to fig. 16, the polarizing films of examples 4, 13 to 15 all overcome the technical problems associated with the manufacture of polarizing films having a thickness of 10 μm or less and have optical characteristics satisfying the required performance required for liquid crystal display devices. The optical properties of each were compared, and the optical properties were increased in the order of example 13 < example 14 < example 4 < example 15. This indicates that: when the auxiliary stretching magnifications in the gas atmosphere of the 1 st stage are all set to 1.8 times, and the stretching magnifications in the boric acid aqueous solution of the 2 nd stage are set only such that the total stretching magnifications increase in the order of 5 times, 5.5 times, 6.0 times, and 6.5 times, the optical properties are improved to such an extent that the final total stretching magnifications are set to higher polarization films. In the process for producing the optical film laminate 10 including the polarizing film 3, the total stretching ratio of the auxiliary stretching in the gas atmosphere of the 1 st stage and the stretching in the boric acid aqueous solution of the 2 nd stage is set to be higher, whereby the optical characteristics of each of the polarizing film to be produced and the optical film laminate including the polarizing film can be remarkably improved.

(7) Improvement in optical characteristics of polarizing film due to Total draw ratio of uniaxial tension at fixed end (examples 16 to 18)

Examples 16 to 18 produced optical film laminates under the same conditions as in example 4, except for the following differences. The difference is the stretching method of auxiliary stretching in a gas atmosphere. In example 4, the free-end uniaxial stretching method was employed, and in examples 16 to 18, the fixed-end uniaxial stretching method was employed. In all of these examples, the auxiliary stretching ratio in the atmosphere of the 1 st stage was set to 1.8 times, and the stretching ratios in the boric acid aqueous solution of the 2 nd stage were set to 3.3 times, 3.9 times, and 4.4 times, respectively. Thus, the total draw ratio was 5.94 times (about 6 times) for example 16, 7.02 times (about 7 times) for example 17, and 7.92 times (about 8 times) for example 18. Except for this point, the production conditions of examples 16 to 18 were completely the same.

Referring to fig. 17, the polarizing films obtained in examples 16 to 18 all overcome the technical problems associated with the production of polarizing films having a thickness of 10 μm or less and have optical characteristics satisfying the required performance required for optical display devices. The respective optical properties were compared, and the optical properties were increased in the order of example 16 < example 17 < example 18. This indicates that: when the auxiliary stretching magnifications in the gas atmosphere of the 1 st stage are all set to 1.8 times, and the stretching magnifications in the boric acid aqueous solution of the 2 nd stage are set such that the total stretching magnifications are increased in the order of 6 times, 7 times, and 8 times, the optical properties are improved to such an extent that the final total stretching magnifications are set to be higher in the polarizing film. In the process for producing the optical film laminate 10 including the polarizing film 3, the total stretching ratio of the auxiliary stretching in the gas atmosphere of the 1 st stage and the stretching in the boric acid aqueous solution of the 2 nd stage in the fixed-end uniaxial stretching method is set to be higher, whereby the optical characteristics of each of the polarizing film to be produced or the optical film laminate including the polarizing film can be remarkably improved. In addition, it was confirmed that: when the fixed-end uniaxial stretching method is used for the auxiliary stretching in the gas atmosphere of the 1 st stage, the final total stretching magnification can be further increased as compared with the case where the free-end uniaxial stretching method is used for the auxiliary stretching in the gas atmosphere of the 1 st stage.

Comparative example 3

In comparative example 3, an aqueous PVA solution was applied to a PET substrate having a thickness of 200 μm under the same conditions as in comparative example 1, and the PET substrate was dried to prepare a laminate having a PVA layer having a thickness of 7 μm formed on the PET substrate. Next, the laminate was immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃. Specifically, the colored laminate is produced by the following method: the laminate is immersed in a dyeing solution containing 0.3 wt% iodine and 2.1 wt% potassium iodide at a liquid temperature of 30 ℃ for an arbitrary period of time, and the monomer transmittance of the finally produced PVA layer constituting the polarizing film is 40 to 44%, whereby iodine is adsorbed in the PVA layer contained in the stretched laminate. Next, the colored laminate including the iodine-adsorbed PVA layer was stretched in an aqueous boric acid solution at a stretching temperature of 60 ℃ to be free-end uniaxially stretched to a stretching ratio of 5.0, thereby producing various optical film laminates including a PVA layer of 3 μm thickness integrally stretched with a PET resin base material.

[ reference example 1]

Reference example 1a laminate having a PVA layer of 7 μm thickness formed on a crystalline PET substrate was prepared by using a continuous belt-like substrate of crystalline polyethylene terephthalate (hereinafter referred to as "crystalline PET") as a resin substrate, applying a PVA aqueous solution to the crystalline PET substrate of 200 μm thickness, and drying the PVA aqueous solution. The glass transition temperature of crystalline PET was 80 ℃. Next, the produced laminate was subjected to free-end uniaxial stretching by high-temperature stretching in a gas atmosphere set at 110 ℃ to a stretching ratio of 4.0 times, thereby producing a stretched laminate. By this stretching treatment, the PVA layer contained in the stretched laminate was converted into a PVA layer having a thickness of 3.3 μm in which the PVA molecules were oriented. In the case of reference example 1, the laminate could not be stretched 4.0 times or more by high-temperature stretching in a gas atmosphere at a stretching temperature of 110 ℃.

The stretched laminate was a colored laminate having iodine adsorbed in a PVA layer having a thickness of 3.3 μm in which PVA molecules were oriented by the following dyeing step. Specifically, the colored laminate is produced by the following method: the stretched laminate is immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary time to adjust the monomer transmittance of the finally produced PVA layer constituting the polarizing film to 40 to 44%, thereby adsorbing iodine in the PVA layer contained in the stretched laminate. In this way, the amount of iodine adsorbed to the PVA layer in which the PVA molecules are oriented was adjusted, and various colored laminates having different monomer transmittances and polarization degrees were produced. Next, the produced colored laminate is subjected to a crosslinking treatment. Specifically, the colored laminate was subjected to crosslinking treatment by immersing the colored laminate in a boric acid crosslinking aqueous solution containing 3 parts by weight of boric acid per 100 parts by weight of water and 3 parts by weight of potassium iodide per 100 parts by weight of water at a liquid temperature of 40 ℃ for 60 seconds. The crosslinked colored laminate of reference example 1 corresponds to the optical film laminate of example 4. Therefore, the washing process, the drying process, the bonding and/or the transferring process are the same as those of example 4.

[ reference example 2]

As a resin substrate, in the same manner as in reference example 1, reference example 2 produced a laminate in which a PVA layer having a thickness of 7 μm was formed on a crystalline PET substrate having a thickness of 200 μm, using a crystalline PET substrate. Next, the produced laminate was subjected to free-end uniaxial stretching by high-temperature stretching in a gas atmosphere at 100 ℃ to a stretching ratio of 4.5 times, thereby producing a stretched laminate. By this stretching treatment, the PVA layer contained in the stretched laminate was converted into a PVA layer having a thickness of 3.3 μm in which the PVA molecules were oriented. In the case of reference example 2, the laminate could not be stretched 4.5 times or more by high-temperature stretching in a gas atmosphere at a stretching temperature of 100 ℃.

Next, a colored laminate was produced from the stretched laminate. The colored laminate was produced by the following method: the stretched laminate is immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary time to adjust the monomer transmittance of the finally produced PVA layer constituting the polarizing film to 40 to 44%, thereby adsorbing iodine in the PVA layer contained in the stretched laminate. Reference example 2 various colored laminates having different monomer transmittances and degrees of polarization were prepared by adjusting the amount of iodine adsorbed to the PVA layer in which the PVA molecules were oriented, as in the case of reference example 1.

[ reference example 3]

As a resin substrate, reference example 3 produced a laminate in which a PVA layer having a thickness of 7 μm was formed on a crystalline PET substrate having a thickness of 200 μm, using the crystalline PET substrate, as in the case of reference example 1 or 2. Next, the laminate thus produced was immersed in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ℃ for an arbitrary period of time, and the monomer transmittance of the PVA layer constituting the polarizing film finally produced was 40 to 44%, thereby producing various colored laminates in which iodine was adsorbed to the PVA layer contained in the laminate. Then, the produced colored laminate was subjected to free-end uniaxial stretching at a high temperature of 90 ℃ in a gas atmosphere to adjust the stretching ratio to 4.5 times, thereby producing a stretched laminate comprising a PVA layer having iodine adsorbed therein corresponding to a polarizing film from the colored laminate. By this stretching treatment, the iodine-adsorbed PVA layer contained in the stretched laminate produced from the colored laminate was converted into a PVA layer having a thickness of 3.3 μm in which the PVA molecules were oriented. In the case of reference example 3, the laminate could not be stretched 4.5 times or more by high-temperature stretching in a gas atmosphere at a stretching temperature of 90 ℃.

[ measurement method ]

[ measurement of thickness ]

The thicknesses of the amorphous PET base material, the crystalline PET base material, and the PVA layer were measured by a digital micrometer (KC-351C manufactured by anritsu Co., Ltd.).

[ measurement of transmittance and degree of polarization ]

The single transmittance T, parallel transmittance Tp, and perpendicular transmittance Tc of the polarizing film were measured by an ultraviolet-visible spectrophotometer (V7100 manufactured by japan spectrophotometers). These T, Tp and Tc are Y values measured in a two-dimensional field of view (C light source) according to JIS Z8701 and corrected for visibility.

The polarization degree P is obtained by the following equation using the transmittance.

Polarization degree P (%) { (Tp-Tc)/(Tp + Tc) }^1/2×100

(method of evaluating orientation function of PET)

The measurement apparatus used was a Fourier transform infrared spectrophotometer (FT-IR) (product name: SPECTRUM 2000, manufactured by Perkin Elmer Co., Ltd.). Using polarized light as measuring light, and using attenuated total reflection spectroscopy (ATR)lreflection) was measured, and the surface of the PET resin layer was evaluated. The calculation of the orientation function is performed in the following order. The measurements were performed in the state where the measurement polarized light was at 0 ° and 90 ° to the stretching direction. The spectrum obtained was used at 1340cm^-1The absorption intensity of (b) is calculated from the following (formula 4) (non-patent document 1). When f is 1, the film is completely oriented, and when f is 0, the film is random. In addition, 1340cm can be said^-1The peak at (a) is the absorption due to the methylene group of the ethylene glycol unit in PET.

(formula 4) f ═ 3 < cos²θ＞－1)/2

＝[(R－1)(R₀+2)]/[(R+2)(R₀－1)]

＝(1－D)/[c(2D+1)]

＝－2×(1－D)/(2D+1)

Wherein

c＝(3cos²β－1)/2

β＝90deg

θ: angle of molecular chain to stretching direction

β Angle of transition dipole moment to molecular chain axis

R₀＝2cot²β

1/R＝D＝(I⊥)/(I//)

(the higher the degree of orientation of PET, the larger the D value.)

I ⊥ absorption intensity measured by incidence of polarized light from a direction perpendicular to the stretching direction

I//: absorption intensity measured by incident polarized light from a direction parallel to the stretching direction

(method of evaluating orientation function of PVA)

The measurement apparatus used was a Fourier transform infrared spectrophotometer (FT-IR) (product name: "SPECTRUM 2000" manufactured by Perkin Elmer Co., Ltd.). The surface of the PVA resin layer was evaluated by attenuated total reflection spectroscopy (ATR) measurement using polarized light as measurement light. The calculation of the orientation function is performed in the following order. The measurements were performed in the state where the measurement polarized light was at 0 ° and 90 ° to the stretching direction. The spectrum obtained was used at 2941cm^-1The absorption intensity of (b) was calculated according to the above (formula 4). The following strength I was 3330cm^-12941cm was used as a reference peak^-1/3330cm^-1The value of (c). When f is 1, the film is completely oriented, and when f is 0, the film is random. In addition, 2941cm can be said^-1The peak at (A) is due to the main chain (-CH) of PVA₂-) absorption by vibration.

(method of evaluating crystallinity of PVA)

The measurement apparatus used was a Fourier transform infrared spectrophotometer (FT-IR) (product name: SPECTRUM 2000, manufactured by Perkin Elmer Co., Ltd.). The surface of the PVA resin layer was evaluated by attenuated total reflection spectroscopy (ATR) measurement using polarized light as measurement light. The crystallinity was calculated in the following order. The measurements were performed in the state where the measurement polarized light was at 0 ° and 90 ° to the stretching direction. 1141cm using the obtained spectrum^-1And 1440cm^-1The intensity of (d) was calculated according to the following equation. 1141cm was confirmed in advance^-1The intensity level at (A) has a correlation with the amount of crystalline fraction, at 1440cm^-1As a reference peak, the crystallization index (formula 6) was calculated according to the following formula. Further, a calibration curve of the crystallinity index and the crystallinity is prepared in advance from a PVA sample having a known crystallinity, and the crystallinity is calculated from the crystallinity index using the calibration curve (formula 5).

Crystallinity (63.8 × (crystallinity index) -44.8 (formula 5)

Crystallization index ═ I ((I (1141 cm)^-1)0°2×I(1141cm^-1)90°)/3)/((I(1440cm^-1)0°+2×I(1440cm^-1)90 degree/3) (type 5)

Wherein the content of the first and second substances,

I(1141cm^-1)0 degree: 1141cm when measured from incident polarized light in the stretching direction and the parallel direction^-1Strength of the spot

I(1141cm^-1)90 degrees: jaw 1141cm in measurement by incidence of polarized light in the stretching direction and the vertical direction^-1Strength of the spot

I(1440cm^-1)0 degree: 1440 measured by measuring incident polarized light from the stretching direction and the parallel directioncm^-1Strength of the spot

I(1440cm^-1)90 degrees: 1440cm in measurement by incidence of polarized light from the stretching direction and the perpendicular direction^-1Strength of the spot

[ use example of polarizing film ]

Fig. 11 and 12 show an embodiment of an optical display device using the polarizing film, by way of example.

Fig. 11a is a cross-sectional view showing one of the most basic embodiments of an organic EL display device, and the display device 200 includes an optical display panel 201 as an organic EL display panel, and a polarizing film 203 is bonded to a surface of the display panel 201 side via an optically transparent pressure-sensitive adhesive layer 202. The outer surface of the polarizing film 203 is bonded 1/4 with a wavelength phase difference film 204. As shown by the broken line, a transparent window 205 may be optionally provided outside the 1/4 wavelength phase difference film 204. This structure is useful for the case of using polarized sunglasses.

Fig. 11B is a cross-sectional view showing another embodiment of the organic EL display device, in which the display device 200a has an optical display panel 201a as an organic EL display panel, and on a surface on the display panel 201a side, 1/4 a of a wavelength retardation film 204a is bonded through an optically transparent adhesive layer 202 a. A polarizing film 203a is bonded to the outer surface of the 1/4 wavelength retardation film 204 a. A protective layer 206 is further adhered to the outer surface of the polarizing film 203 a. As shown by the dotted line, a transparent window 205a may be optionally provided outside the protective layer 206, which is the viewing side of the optical display device 200 a. In this embodiment, the external light that has been linearly polarized by the polarizing film 203a is converted into circularly polarized light by the 1/4 wavelength phase difference film 204 a. This structure is effective for preventing internal reflection of external light, since external light can be prevented from being reflected by the front surface and the back surface electrode of the optical display panel 201a, other internal reflection surfaces, and the like and returned to the viewing side of the optical display device 200 a.

As a material for joining or bonding the layers, films, and the like, for example, a material having a polymer as a base polymer, such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based, an isocyanate, a polyvinyl alcohol, a gelatin-based, a vinyl latex-based, or a water-based polyester, can be appropriately selected and used.

As described above, the thickness of the polarizing film 203 is 10 μm or less, and the aforementioned optical properties are satisfied. Since the polarizing film 203 is very thin as compared with a conventional polarizing film used for an optical display device, stress due to expansion and contraction under temperature or humidity conditions is extremely small. Therefore, the possibility that the adjacent display panel 201 is deformed such as warped by the stress generated by the shrinkage of the polarizing film is greatly reduced, and the reduction in display quality due to the deformation can be greatly suppressed. In this structure, as the adhesive layer 202, a material having a diffusion function can be used, or a 2-layer structure of an adhesive layer and a diffusing agent layer can be made.

As a material for improving the adhesive strength of the pressure-sensitive adhesive layer 202, for example, a tack coat layer described in japanese patent laid-open nos. 2002-258269 (patent document 12), 2004-078143 (patent document 13), and 2007-171892 (patent document 14) may be provided. The binder resin is not particularly limited as long as it is a layer capable of improving the anchoring force ( force application) of the binder, and specifically, for example, epoxy resins, isocyanate resins, polyurethane resins, polyester resins, polymers containing amino groups in the molecule, epoxy resins, isocyanate,Ester carbamates(エステルウレタン) a resin composition comprising

Resins (polymers) having an organic reactive group such as various acrylic resins such as oxazoline group.

In addition, an antistatic agent may be added to the anchor coat layer in order to impart antistatic properties, as described in, for example, japanese patent application laid-open No. 2004-338379 (patent document 15). As antistatic agents for imparting antistatic properties, there can be mentioned: ionic surfactants, and conductive polymers such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline; metal oxides such as tin oxide, antimony oxide, and indium oxide, and the like, but conductive polymers are particularly preferably used in view of optical properties, appearance, antistatic effect, and stability of antistatic effect in heating and humidifying. Among them, a water-soluble conductive polymer such as polyaniline and polythiophene, or a water-dispersible conductive polymer is particularly preferably used. When a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, the modification of the optical film substrate material by an organic solvent at the time of coating can be suppressed.

Fig. 12 shows an embodiment of an optical display device 300 having a transmissive liquid crystal display panel 301 as an optical display panel. In this structure, a 1 st polarizing film 303 is bonded to the viewing side surface of the liquid crystal display panel 301 via an adhesive layer 302, and a protective layer 304 is bonded to the 1 st polarizing film 303 via an easy-adhesion layer 307. The 1/4 wavelength retardation layer 309 is bonded on the protective layer 304. An antistatic layer 308 is optionally formed on the 1/4 wavelength retardation layer 309. A window 305 is optionally provided outside the 1/4 wavelength retardation layer 309. On the other side face of the liquid crystal display panel 301, a 2 nd polarizing film 303a is provided through a 2 nd adhesive layer 302 a. On the back surface of the 2 nd polarizing film 303a, a backlight 310 is provided as is well known for transmissive liquid crystal display devices.

[ embodiments of the invention ]

Next, an embodiment of manufacturing an optical film laminate that can be used in the present invention will be described with reference to fig. 30. As shown in fig. 9 or fig. 10, a thermoplastic resin substrate 1 made of, for example, amorphous PET is subjected to the following operations to produce an optical film laminate 400 in which a polarizing film 3 having a thickness of 10 μm or less, specifically, 3 to 4 μm is formed on the substrate 1, and then the optical film laminate is sent out of a stretching apparatus, the operations including: film formation by the laminate production apparatus 20, auxiliary stretching in an air atmosphere in the oven 30, dyeing with a 2-color dye by the dyeing apparatus 40, and underwater stretching in the boric acid aqueous solution tank 50. Here, the optical film laminate 400 may be wound in a roll form or may be directly and continuously fed to the next step. As the next step, the optical film laminate forming apparatus shown in fig. 30 includes a separation film bonding unit 500 and a defect inspection unit 600.

The separation film laminating unit 500 has a pair of laminating rollers 501 and 502. In the separation film laminating unit 500, the optical film laminate 400 is fed between the laminating rollers 501 and 502 with the polarizing film 3 positioned on the lower side. The separation film 503 is continuously drawn from the winding core 503a of the separation film 503, and is fed between the bonding rollers 501 and 502 in a state of being overlapped with the lower side of the optical film laminate 400. Before the optical film laminate 400 and the separation film 503 are fed between the bonding rollers 501 and 502, an adhesive 504a is applied in the form of a layer between the laminated optical film laminate 400 and the separation film 503. Therefore, when the optical film laminate 400 and the separation film 503 come out from the bonding rollers 501 and 502, the separation film 503 is laminated on the surface of the polarizing film 3 of the optical film laminate 400 with the adhesive layer 504 interposed therebetween, thereby forming the separation film-attached optical film laminate 510. In this step, the optical film laminate 510 with the separation film may be temporarily wound into a roll. The surface of the separation film 503 facing the pressure-sensitive adhesive layer 504 is subjected to a release treatment, and the adhesion between the separation film 503 and the pressure-sensitive adhesive layer 504 is weaker than the adhesion between the polarizing film 3 and the pressure-sensitive adhesive layer 504. Therefore, as described later, when the separation film 503 is peeled off from the optical film laminate 400, the adhesive layer 504 remains on the optical film laminate 400 side. The adhesive layer 504 can be used as an adhesive layer when the optical film laminate 400 is bonded to another member such as a display panel.

The defect inspection unit 600 has a reference point printing device 610 that prints a reference point mark M on the surface of the base material 1 of the optical film laminate 510 with a separation film. The reference point printing means 610 gives a mark, which becomes a positional reference in the longitudinal direction of the optical film laminated body with separation film 510, to an appropriate position in the vicinity of the leading end (guide end) in the conveyance direction of the optical film laminated body with separation film 510.

In the example shown in fig. 30, the optical film laminate 510 with the separation film fed out from the pair of bonding rollers 501, 502 is directly fed to and passes through the reference point printing device 610. A conveyance amount measuring device constituted by a length measuring roller 611 is provided on the downstream side of the printing device 610. The length measuring roller 611 measures the amount of conveyance of the optical film laminate with the separation film fed to and passed through the length measuring roller 611 by the amount of rotation thereof, and sends a measurement signal to a laminate conveyance amount calculation device 620a of a storage calculation unit 620 provided in the optical film laminate forming apparatus.

The defect inspection unit 600 has a separation film peeling section 601 on the downstream side in the conveyance direction of the length measurement roller 611. The separation film peeling section 601 includes: a pair of guide rollers (602, 603), a peeling film guide roller 604 that guides the peeled separation film 503, and a winding roller 605 that winds the peeled separation film 503. The optical film laminate 400 from which the separation film 503 has been peeled off has a form in which the pressure-sensitive adhesive layer 504 remains on the surface of the polarizing film 3. The optical film laminate 400 having the adhesive layer 504 is sent to a defect inspection section 630. The defect inspection section 630 includes: a reference point reading mechanism 631, and a transmitted light detection type optical defect detection mechanism including a light source 632 and a light detection member 633. The read signal from the reference point reading means 631 is sent to the reference point reading time storage means 620b of the storage operation unit 620, and the time when the reference point is detected is stored. The defect detection signal sent from the optical defect detection means is sent to the defect detection time calculation means 620c of the storage calculation unit 620, and the defect detection time calculation means 620c calculates and stores the time when the defect is detected. Signals from the stacked body conveyance amount calculation means 620a, the reference point reading time storage means 620B, and the defect detection time calculation means 620c are input to a defect position calculation unit 672 of the control device 670 provided in the optical film stacked body forming apparatus, and the defect position calculation unit 672 calculates the position of the defect from the reference point mark M by receiving these input data, and sends a defect position signal to a defect mark print instruction generation unit 620d of the storage calculation unit 620.

The optical film laminate 400 passed through the defect inspection unit 600 then passes through the separation film attaching unit 640. The separation film bonding unit 640 has bonding rollers 641 and 642 for bonding the separation film 503 continuously drawn out from the winding core 503a of the separation film 503 to the optical film laminate 400 through the adhesive layer 504 remaining on the polarizing film 3 of the optical film laminate 400. The optical film laminate 400 fed out from the bonding rollers 641 and 642 is a separation film-attached optical film laminate 510 to which the separation film 503 is bonded. Here, as the separation film 503 to be bonded, a separation film peeled at the separation film peeling section 620 may be used, or a separately prepared separation film may be used.

The optical film laminate 510 with the separation film fed out from the bonding rollers 641 and 642 is passed through the 2 nd defect inspection unit 650 which is set arbitrarily. The 2 nd defect inspection unit 650 has a reference point detection mechanism 651 and an optical defect detection mechanism 652. The optical defect detection mechanism 652 is constituted by a light source 652a that irradiates light to the surface of the separation film 503 of the optical film laminate with separation film 510, and a light receiving portion 652b that receives reflected light from the surface of the separation film 503. The optical defect detection mechanism 652 detects a surface defect of the separation film 503 and a defect contained in the adhesive layer 504 in the optical film laminate 510 with a separation film. The detection signal of the reference point detecting mechanism 651 is sent to the reference point reading time storing mechanism 620b, and the detection signal of the light receiving portion 652b is sent to the defect detection time operating mechanism 620 c.

The optical film laminate 510 with the separation film passed through the 2 nd defect inspection unit 650 is sent to and passed through a conveyance amount measuring device having a length measuring roller 660, and the conveyance amount of the laminate 510 is measured. A signal indicating the measured transfer amount is sent to the reference point check unit 671 of the control unit 670 provided in the optical film laminate forming apparatus. A reference point reading mechanism 661 is provided on the downstream side of the length measuring roller 660, the reference point reading mechanism 661 reads a mark M of a reference point formed on the optical film laminate 400, and a signal of information on the timing at which the mark M passes is sent to a reference point checking section 671 of the control device 670. The reference point checking section 671 receives signals from the length-measuring roller 660 and the reference point reading mechanism 661, and inputs a signal relating to the conveyance amount of the stacked body from the reference point mark M to the defective print instruction generating section 620d of the storage arithmetic mechanism 620. The defect print instruction generating section 620D generates a print instruction to print the defect mark D at the defect position on the optical film laminate 510 with the separation film based on the defect position signal from the defect position calculating section 672 and the conveying amount signal from the reference point collating section 671. The print instruction is sent to a mark printing device 662 provided on the downstream side of the reference point reading mechanism 661, and the mark printing device 662 is operated to print a defect mark D at a position corresponding to a defect on the thermoplastic resin base material of the optical film laminate 510 with the separation film. The printed optical film laminate 510 with the separation film is wound into a roll 680.

In the above embodiment, the defect position is described as being printed with the defect mark D on the stacked body 510, but a method may be used instead in which an identification mark for identifying the roll is provided on the roll 680 of each stacked body 510, and the defect position is associated with the identification mark for identifying the roll 680 of the stacked body 510 and stored in the storage arithmetic unit 620. In such a configuration, in a subsequent step of a roll 680 using the optical film laminate 510, the defective position of the roll is read out by the memory operation unit based on the identification mark of the roll, and the defective position of the optical film laminate can be identified.

Fig. 31 is a schematic view of the same manufacturing process of the optical laminate roll as in fig. 30 showing another embodiment of the present invention. In fig. 31, portions corresponding to those in the embodiment of fig. 30 are denoted by the same reference numerals as in fig. 30, and descriptions thereof are omitted. The embodiment of fig. 31 differs from the embodiment of fig. 30 in that: before the separation film 503 is bonded to the polarizing film 3 side of the optical film laminate 400, the optical functional film 800 is bonded to the surface of the polarizing film 3 with an adhesive 801. The optical functional film 800 may be the 1/4 wavelength retardation film, the viewing angle compensation film, and the optical compensation film used in the art, which are described above. The optical functional film 800 is continuously drawn from a roll 800a, fed by a guide roller 802, and bonded to the optical film laminate 400 by a pair of bonding rollers 803 and 804, thereby producing an optical film intermediate laminate 510 a. Therefore, in this embodiment, the separation film 503 is bonded to the optical functional film 800 with the adhesive layer 504, thereby forming the optical film laminate 510 b. Other aspects of this embodiment are the same as the embodiment shown in fig. 30.

Unlike the embodiment shown in fig. 31, the embodiment shown in fig. 32 is different in that the separating film 503 is not bonded to the polarizing film 3 side of the optical film laminate 400, and instead, the optical functional film 800 is bonded to the surface of the polarizing film 3 with an adhesive 801. After the optical functional film 800 is bonded, the thermoplastic resin base material 1 used for stretching is peeled from the polarizing film 3 by peeling rollers 810 and 811, and an optical film intermediate laminate 510c is formed. The peeled substrate 1 is wound around a roller 813 via a guide roller 812.

In the optical film intermediate laminate 510c from which the base material 1 is peeled, a mark M indicating a reference point is printed on the surface of the optical functional film 800 by the reference point printing mechanism 610. Next, the optical film intermediate laminate 510c is fed to the separation film laminating unit 500A by the length measuring roller 611. In the separation film laminating unit 500A, the separation film 503 continuously drawn from the roll 503a of the separation film 503 is fed to be overlapped with the surface of the optical film intermediate laminate 510c from which the substrate 1 is peeled, and is laminated to the polarizing film 3 by the laminating rollers 501 and 502 via the adhesive 504a, thereby forming the optical film laminate 510 d.

The separation film 503 is peeled off from the optical film laminate 510d at the position passed through the peeling rollers 602 and 603, and the pressure-sensitive adhesive layer 504a is attached to the polarizing film 3 of the optical film intermediate laminate 510 c. The laminate passes through the defect inspection unit 630 and is sent to the separation film bonding unit 640, and in the unit 640, the separation film 503 is bonded to the laminate via the adhesive layer 504 on the polarizing film 3 side of the laminate, thereby forming the optical film laminate 510 d. Otherwise, the embodiment shown in fig. 32 is the same as that of fig. 31.

Fig. 33 is the same view as fig. 32 showing another embodiment of the present invention. This embodiment differs from the embodiment shown in fig. 32 in that: before the separation film 503 is bonded to the surface of the laminate from which the substrate 1 has been peeled, the 2 nd optical functional film 850 is bonded to the surface of the polarizing film of the laminate from which the substrate 1 has been peeled with an adhesive 851. The 2 nd optical functional film 850 is continuously drawn from the roll 850a and fed by the guide roller 852, and is bonded to the laminate 510c by the pair of bonding rollers 803a and 804a, thereby forming the optical film intermediate laminate 510 e. In this embodiment, the separation film 503 is bonded to the 2 nd optical functional film 850 with the adhesive layer 504a interposed therebetween to form an optical film laminate 510 f. Although the reference point printing device 610 and the length-measuring roller 611 are provided on the downstream side of the attaching rollers 501, 502 for attaching the separation film 503, the functions thereof are the same.

Fig. 34 is a schematic view showing an example of a continuous laminating apparatus for laminating a laminate on a liquid crystal display panel using the optical film laminate with a separation film formed by the above-described method, for example, a roll 680 of the laminate 510d shown in fig. 32. In this case, the separation membrane 503 in fig. 32 is a carrier membrane. Therefore, in the following description, the film denoted by reference numeral 503 is referred to as a carrier film, and a laminate in which the carrier film 503 is laminated is referred to as a carrier-film-attached laminate.

The continuous laminating device is composed of: in the step of manufacturing the roll 680, the slit cutting position on the optical film laminate 510d is determined in advance based on the detected defect information, and the cutting position information is stored in the storage means.

As shown in FIG. 35, the cut position S is determined at a position separated from the position of the defect D by a predetermined distance D1 and D2 on the upstream side and the downstream side in the transport direction, respectively, the region between 2 cut positions sandwiching the defect D is a region including a defective piece Sd, and the cut position is determined at a distance corresponding to one of the long side or short side dimensions of the liquid crystal display panel to which the laminate 510D is bonded in the region not including the defect.

The operation of the incision position can be performed by, for example, a control device 670 shown in the apparatus shown in fig. 32. The calculated slit position information can be stored in the information medium 690 shown in fig. 32 together with the identification information for identifying the roll 680 of the laminate 510 d. As shown in fig. 34, the control device 400 of the continuous laminating device can receive the identification information and the slit-cutting position information from the information medium 690 of the device shown in fig. 32. The received identification information and the slit-cut position information are stored in the storage device 420 in the control device 400 of the continuous laminating apparatus shown in fig. 34.

The continuous laminating apparatus includes a roll supporting device 110 for rotatably supporting a roll 680 of the stacked body 510d, and the stacked body 510d is fed from the roll 680 at a predetermined transport speed by driving the roll 680 of the stacked body 510d supported by the roll supporting device 110 at a predetermined speed in a stacked body feeding direction. The optical film laminate 510d with the separation film fed from the roll 680 passes through the identification information reading device 120 and passes through the length measuring rollers 130 and 131. The identification information reading device 120 reads the identification information of the stacked body 510d continuously drawn from the roll 680, and sends the read identification information to the identification information receiving unit 410 of the control device 400. The conveyance amount of the stacked body 510d is measured by the length measuring rollers 130 and 131, and information on the measured conveyance amount is sent to the control device 400 as continuous extraction information.

The laminate 510d having passed through the length measuring rolls 130 and 131 is sent to the slit cutter unit a through an Accu Roll mill 140, and the Accu Roll mill 140 is supported so as to be movable up and down and elastically biased downward with a predetermined force. A feed roller (feed roller) 170 is provided downstream of the slit cutting unit a to feed the stacked body 510d at a predetermined speed, and the stacked body 510d is stopped at the slit cutting unit a by stopping the feed roller 170 at a short moment when the slit is cut. A 2Accu Roll mill 180 is provided downstream of the feed rolls 170. The structure of the AccuRoll mill 180 is the same as that of the Accu Roll mill 140.

The incision cutting unit a includes: a slit cutter 150, and a cutting position confirmation device 160 provided on the upstream side and the downstream side of the slit cutter 150. The control device 400 receives the confirmation signal from the cutting position confirmation device 160, obtains the slit cutting position information from the roll identification information from the identification information reading device 120 and the defect information stored in the storage means 420, and sends a cutting command to the slit cutting device 150. When the slit cutter 150 is operated to form a slit in the optical film laminate 510d, the feed roller 170 is operated to restart the feeding of the optical film laminate 510d with the carrier film. As described above, the optical film laminate 510d with the carrier film is continuously conveyed and driven on the upstream side of the Accu Roll mill 140, and when the cutting unit a stops the conveyance of the laminate to perform the slit cutting, the Accu Roll mills 140 and 180 move up and down to absorb the difference in the conveyance amount of the laminate.

The slit formed by slit-cutting in the slit-cutting unit a has the following depth: the optical film sheets are formed between 2 slits adjacent in the transport direction from the side of the optical film laminate 510d with the separation film opposite to the carrier film 503 to a depth reaching the interface between the carrier film 503 and the adhesive layer 504. The sheet is sent to the next step while being supported by the carrier film 503. The sheet thus formed is a defective sheet Sd when it contains a defect D, and a normal sheet Sn when it does not contain a defect.

The stacked body 510d after passing through the 2Accu Roll mill 180 then passes through the defective sheet removal unit C. In the eliminating unit C, the control device 400 sends out information on the defective pieces Sd, and upon receiving the information, the eliminating device 190 included in the eliminating unit C operates to discharge the defective pieces Sd out of the conveying path. The removing device 190 includes a receiving film roller (receiving フィルムロール)190b for feeding out the defective sheet receiving film 190a, and a take-up roller (take-up りロール)190d for taking back the defective sheet receiving film 190a pulled out by the receiving film roller 190 b. The defective sheet receiving film 190a is sent from the receiving film roller 190b to the pickup roller 190d via the guide roller 190 c. The pickup roller 190d is a driving roller that is driven and operated when the defective sheet Sd reaches the vicinity of the removing device 190, and conveys the defective sheet receiving film 190a in the direction indicated by the arrow in fig. 34. A stack path moving roller 190e is provided on the conveyance path of the stack 510d, and the stack path moving roller 190e and the guide roller 190c are opposed to each other with the stack 510d interposed therebetween, and the stack path moving roller 190e is movable in the left direction in fig. 34. When the defective sheet Sd reaches the vicinity of the removing device 190 and the take-up roller 190d starts operating, the path moving roller 190e moves in the left direction, and the conveyance path of the laminate is changed until the laminate 510d comes into contact with the guide roller 190 c. By the movement of the path, the defective sheet Sd on the carrier film is transferred to the defective sheet receiving film 190 a. Thus, the defective sheet is removed, the pickup roller 190d is stopped, and the path moving roller 190e returns to the first position in the right direction.

The laminate 510d with the carrier film after passing through the defective sheet removal unit C is sent to the bonding unit B via a straight state check device 230 for checking whether or not the laminate is in a straight state. The liquid crystal display panel W is fed to the bonding unit at the same time as the normal sheet Sn is fed to the bonding unit B. The liquid crystal display panels W are fed out 1 by 1 from a panel rack (rack) of the conveyor, and are sent to the bonding unit B by the liquid crystal display panel conveying mechanism 300.

In the bonding unit B, the normal sheet Sn of the optical film laminate is peeled off from the carrier film 503 and conveyed, and is superimposed on the liquid crystal display panel W fed to the bonding unit B. The laminating unit B is provided with a laminating device 200, and the laminating device 200 is constituted by a lower laminating roller 200a and an upper laminating roller 200B, the lower laminating roller 200a is provided at a position below the liquid crystal display panel W sent to the laminating unit B, and the upper laminating roller 200B is located above the optical film laminate normal sheet Sn sent to the laminating unit B. The upper bonding roller 200b can move up and down as shown by a dotted line in fig. 34.

The bonding unit B is provided with a normal sheet leading end detection device 220 capable of detecting that the normal sheet Sn has reached the bonding position. When the normal sheet Sn is detected to have reached the bonding position, the upper bonding roller 200b is lowered to the position shown by the solid line in fig. 34, and the normal sheet is bonded to the liquid crystal display panel W. When the normal sheet Sn is peeled off from the carrier film 503, the pressure-sensitive adhesive layer 504 in which the optical film laminate is bonded to the carrier film is left on the normal sheet Sn side, and the normal sheet Sn is bonded to the liquid crystal display panel W via the pressure-sensitive adhesive layer 504.

The peeling mechanism for peeling the normal sheet Sn from the carrier film has a peeling member 211, and the peeling member 211 has a leading edge portion at an acute angle. The peeling member 211 acts to fold the peeled carrier film 503 at an acute angle by the leading edge portion, and the folded carrier film 503 is retrieved in the right direction by the take-up roller 212 as shown in fig. 34 and wound around the roller 210. When the normal sheet Sn peeled off from the carrier film 503 has sufficient rigidity, the normal sheet Sn is directly conveyed in the conveying direction and reaches the bonding position.

Fig. 36 shows an example of a problem that occurs in the case of a very thin laminate having insufficient rigidity, such as the optical film laminate used in the present invention. When the normal sheet Sn of the optical film laminate is peeled from the carrier film 503 by the edge portion of the distal end of the peeling member 211, the distal end thereof is bent downward by gravity, and wrinkles are generated.

The present invention provides a method for solving the above-described problems occurring when a thin optical film laminate is used, and an example of one embodiment thereof is shown in fig. 37(a) and (b). In fig. 37(a), a vacuum suction roller 213 is provided at a position close to the leading edge portion of the peeling member 211 and in contact with the upper side of the normal sheet Sn. The vacuum suction roller 213 contacts and holds the normal sheet Sn peeled off from the carrier film 503, and guides the normal sheet Sn to travel to a normal conveyance path. Fig. 37(b) shows an example in which a vacuum suction plate 213a is provided instead of the vacuum suction roller 213. In this example, the normal sheet Sn is lifted up by the vacuum suction plate 213a, slid down along the lower surface of the plate 213a, and reaches the bonding position.

Fig. 38 shows an example in which the upper bonding roll 200b of the bonding apparatus 200 is used as a vacuum suction roll, and the operation sequence thereof is shown in (a), (b), and (c). In fig. 38(a), the upper bonding roller 200b holds the leading end of the normal sheet Sn peeled from the carrier film 503 by suction force while descending downward. Next, as shown in fig. 38(b), the upper bonding roller 200b is lowered to the bonding position, and as shown in fig. 38(c), the normal sheet Sn is bonded to the liquid crystal display panel W.

Fig. 39 shows another embodiment, in this example, the normal sheet Sn peeled off from the peeling member 211 is adsorbed on the upper bonding roller 200b provided in the form of a vacuum suction roller as in the example of fig. 38 by the action of the vacuum suction force, and the peeling member 211 can be provided in the form of a guide roller. Thus, the normal sheet Sn is wound around the upper bonding roller 200b by half a rotation to the right, and is fed to the bonding position in a state of being overlapped with the liquid crystal display panel W. At this time, the normal sheet Sn is pressed and attached to the liquid crystal display panel W.

As described above with reference to fig. 37 to 39, it is preferable that at least the front end portion in the moving direction of the optical film normal sheet is sucked by a vacuum suction action just before reaching the bonding position, the optical film normal sheet is superimposed on the display panel fed to the bonding position, and the display panel and the optical film normal sheet are bonded to each other through the adhesive layer remaining on the normal sheet, whereby bonding can be performed without any trouble even when a thin optical film laminate is used. Therefore, according to the present invention, continuous production of an optical display device can be realized with high work efficiency using a thin optical film laminate.

While the specific embodiments of the present invention have been described above with reference to the drawings, the present invention may be variously modified in addition to the illustrated and described configurations. Accordingly, the invention is not limited to the constructions shown and described, but instead its scope is to be determined by the claims appended hereto and their corresponding scope.

Claims (2)

1. A laminating apparatus for laminating an optical film laminate with a carrier film on a rectangular panel having a long side and a short side in this order, the optical film laminate with the carrier film being composed of an optical film and a carrier film, the optical film comprising at least a polarizing film, the carrier film being laminated to the optical film via an adhesive layer, the adhesive force between the carrier film and the adhesive layer being weaker than that between the optical film and the adhesive layer, the polarizing film having a thickness of 10 [ mu ] m or less,

the laminating device is provided with:

a roll supporting device for supporting the roll of the optical film laminated body with the carrier film so as to be freely rotatable;

a slit forming mechanism that sequentially forms a plurality of slits in a width direction of the optical film laminate with the carrier film fed from a roll supported by a roll supporting device, the plurality of slits having a distance in a longitudinal direction corresponding to one of the long side dimension and the short side dimension of the panel, the slits having a depth from a surface of the optical film on a side opposite to the carrier film to a surface of the carrier film adjacent to the optical film, and forms an optical film sheet supported by the carrier film between 2 slits adjacent in the longitudinal direction;

a bonding mechanism having a lower bonding roller provided at the bonding position and an upper bonding roller movable in a vertical direction, for bonding the optical film to the panel;

a feeding mechanism that feeds the optical film laminate with the carrier film, on which the slit is formed, to the bonding position;

the panel conveying mechanism sequentially conveys the panel and the optical film to be conveyed to the bonding position synchronously; and

a peeling mechanism that peels the optical film sheet from the carrier film in a state where the pressure-sensitive adhesive layer remains on the optical film sheet side immediately before the bonding position,

wherein the content of the first and second substances,

the peeling mechanism and the bonding mechanism are arranged so that the optical film sheet peeled from the carrier film by the peeling mechanism is fed between a lower side of the upper bonding roller and an upper side of the lower bonding roller of the bonding mechanism,

the upper bonding roller of the bonding mechanism is configured as a vacuum suction roller, and at least the front end portion of the optical film sheet in the moving direction is sucked from the upper side of the sheet by a vacuum suction action in the process of descending downward, and the optical film sheet is overlapped with the panel sent to the bonding position, and the panel and the optical film sheet are bonded through the adhesive layer.

2. The bonding apparatus according to claim 1, wherein the polarizing film has optical properties satisfying the following conditions when the monomer transmittance is T and the degree of polarization is P:

P＞－(10^{0.929T―42.4}-1) x 100, wherein T < 42.3, and

p is more than or equal to 99.9, wherein T is more than or equal to 42.3,

or optical characteristics satisfying the following conditions:

t is 42.5 or more and P is 99.5 or more.

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